/**************************************************************************
 *
 * Copyright 2013-2014 RAD Game Tools and Valve Software
 * Copyright 2010-2014 Rich Geldreich and Tenacious Software LLC
 * All Rights Reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 **************************************************************************/

/* stbi-1.18 - public domain JPEG/PNG reader - http://nothings.org/stb_image.c
                      when you control the images you're loading

   QUICK NOTES:
      Primarily of interest to game developers and other people who can
          avoid problematic images and only need the trivial interface

      JPEG baseline (no JPEG progressive, no oddball channel decimations)
      PNG 8-bit only
      BMP non-1bpp, non-RLE
      TGA (not sure what subset, if a subset)
      PSD (composited view only, no extra channels)
      HDR (radiance rgbE format)
      writes BMP,TGA (define STBI_NO_WRITE to remove code)
      decoded from memory or through stdio FILE (define STBI_NO_STDIO to remove code)
      supports installable dequantizing-IDCT, YCbCr-to-RGB conversion (define STBI_SIMD)

   TODO:
      stbi_info_*

   history:
      1.18   fix a threading bug (local mutable static)
      1.17   support interlaced PNG
      1.16   major bugfix - convert_format converted one too many pixels
      1.15   initialize some fields for thread safety
      1.14   fix threadsafe conversion bug; header-file-only version (#define STBI_HEADER_FILE_ONLY before including)
      1.13   threadsafe
      1.12   const qualifiers in the API
      1.11   Support installable IDCT, colorspace conversion routines
      1.10   Fixes for 64-bit (don't use "unsigned long")
             optimized upsampling by Fabian "ryg" Giesen
      1.09   Fix format-conversion for PSD code (bad global variables!)
      1.08   Thatcher Ulrich's PSD code integrated by Nicolas Schulz
      1.07   attempt to fix C++ warning/errors again
      1.06   attempt to fix C++ warning/errors again
      1.05   fix TGA loading to return correct *comp and use good luminance calc
      1.04   default float alpha is 1, not 255; use 'void *' for stbi_image_free
      1.03   bugfixes to STBI_NO_STDIO, STBI_NO_HDR
      1.02   support for (subset of) HDR files, float interface for preferred access to them
      1.01   fix bug: possible bug in handling right-side up bmps... not sure
             fix bug: the stbi_bmp_load() and stbi_tga_load() functions didn't work at all
      1.00   interface to zlib that skips zlib header
      0.99   correct handling of alpha in palette
      0.98   TGA loader by lonesock; dynamically add loaders (untested)
      0.97   jpeg errors on too large a file; also catch another stb_malloc failure
      0.96   fix detection of invalid v value - particleman@mollyrocket forum
      0.95   during header scan, seek to markers in case of padding
      0.94   STBI_NO_STDIO to disable stdio usage; rename all #defines the same
      0.93   handle jpegtran output; verbose errors
      0.92   read 4,8,16,24,32-bit BMP files of several formats
      0.91   output 24-bit Windows 3.0 BMP files
      0.90   fix a few more warnings; bump version number to approach 1.0
      0.61   bugfixes due to Marc LeBlanc, Christopher Lloyd
      0.60   fix compiling as c++
      0.59   fix warnings: merge Dave Moore's -Wall fixes
      0.58   fix bug: zlib uncompressed mode len/nlen was wrong endian
      0.57   fix bug: jpg last huffman symbol before marker was >9 bits but less
                      than 16 available
      0.56   fix bug: zlib uncompressed mode len vs. nlen
      0.55   fix bug: restart_interval not initialized to 0
      0.54   allow NULL for 'int *comp'
      0.53   fix bug in png 3->4; speedup png decoding
      0.52   png handles req_comp=3,4 directly; minor cleanup; jpeg comments
      0.51   obey req_comp requests, 1-component jpegs return as 1-component,
             on 'test' only check type, not whether we support this variant
*/

#include "vogl_stb_image.h"

#ifdef COMPILER_MSVC
#pragma warning(disable : 4793) //  function compiled as native
#endif

#ifndef STBI_NO_HDR
#include <math.h>   // ldexp
#include <string.h> // strcmp
#endif

#ifndef STBI_NO_STDIO
#include <stdio.h>
#endif
#include <stdlib.h>
#include <memory.h>
#include <assert.h>
#include <stdarg.h>

namespace vogl
{

    inline void *stb_malloc(size_t c)
    {
        return vogl_malloc(c);
    }
    inline void *stb_realloc(void *p, size_t c)
    {
        return vogl_realloc(p, c);
    }
    inline void stb_free(void *p)
    {
        vogl_free(p);
    }

#if !defined(COMPILER_MSVC) && !defined(COMPILER_MINGW)
#ifdef __cplusplus
#define __forceinline inline
#else
#define __forceinline
#endif
#endif

    // implementation:
    typedef unsigned char uint8_t;
    typedef unsigned short uint16_t;
    typedef signed short int16_t;
    typedef unsigned int uint32_t;
    typedef signed int int32_t;
    typedef unsigned int uint32_t;

    // should produce compiler error if size is wrong
    typedef unsigned char validate_uint32[sizeof(uint32_t) == 4];

#if defined(STBI_NO_STDIO) && !defined(STBI_NO_WRITE)
#define STBI_NO_WRITE
#endif

    //////////////////////////////////////////////////////////////////////////////
    //
    // Generic API that works on all image types
    //

    // this is not threadsafe
    static const char *failure_reason;

    const char *stbi_failure_reason(void)
    {
        return failure_reason;
    }

    static int e(const char *str)
    {
        failure_reason = str;
        return 0;
    }

#ifdef STBI_NO_FAILURE_STRINGS
#define e(x, y) 0
#elif defined(STBI_FAILURE_USERMSG)
#define e(x, y) e(y)
#else
#define e(x, y) e(x)
#endif

#define epf(x, y) ((float *)(e(x, y) ? NULL : NULL))
#define epuc(x, y) ((unsigned char *)(e(x, y) ? NULL : NULL))

    void stbi_image_free(void *retval_from_stbi_load)
    {
        stb_free(retval_from_stbi_load);
    }

#define MAX_LOADERS 32
    stbi_loader *loaders[MAX_LOADERS];
    static int max_loaders = 0;

    int stbi_register_loader(stbi_loader *loader)
    {
        int i;
        for (i = 0; i < MAX_LOADERS; ++i)
        {
            // already present?
            if (loaders[i] == loader)
                return 1;
            // end of the list?
            if (loaders[i] == NULL)
            {
                loaders[i] = loader;
                max_loaders = i + 1;
                return 1;
            }
        }
        // no room for it
        return 0;
    }

#ifndef STBI_NO_HDR
    static float *ldr_to_hdr(stbi_uc *data, int x, int y, int comp);
    static stbi_uc *hdr_to_ldr(float *data, int x, int y, int comp);
#endif

#ifndef STBI_NO_STDIO
    unsigned char *stbi_load(char const *filename, int *x, int *y, int *comp, int req_comp)
    {
        FILE *f = fopen(filename, "rb");
        unsigned char *result;
        if (!f)
            return epuc("can't fopen", "Unable to open file");
        result = stbi_load_from_file(f, x, y, comp, req_comp);
        fclose(f);
        return result;
    }

#ifdef COMPILER_MSVC
    unsigned char *stbi_load_w(wchar_t const *filename, int *x, int *y, int *comp, int req_comp)
    {
        FILE *f = _wfopen(filename, L"rb");
        unsigned char *result;
        if (!f)
            return epuc("can't fopen", "Unable to open file");
        result = stbi_load_from_file(f, x, y, comp, req_comp);
        fclose(f);
        return result;
    }
#endif

    unsigned char *stbi_load_from_file(FILE *f, int *x, int *y, int *comp, int req_comp)
    {
        int i;
        if (stbi_jpeg_test_file(f))
            return stbi_jpeg_load_from_file(f, x, y, comp, req_comp);
        if (stbi_png_test_file(f))
            return stbi_png_load_from_file(f, x, y, comp, req_comp);
        if (stbi_bmp_test_file(f))
            return stbi_bmp_load_from_file(f, x, y, comp, req_comp);
        if (stbi_psd_test_file(f))
            return stbi_psd_load_from_file(f, x, y, comp, req_comp);
#ifndef STBI_NO_HDR
        if (stbi_hdr_test_file(f))
        {
            float *hdr = stbi_hdr_load_from_file(f, x, y, comp, req_comp);
            return hdr_to_ldr(hdr, *x, *y, req_comp ? req_comp : *comp);
        }
#endif
        for (i = 0; i < max_loaders; ++i)
            if (loaders[i]->test_file(f))
                return loaders[i]->load_from_file(f, x, y, comp, req_comp);
        // test tga last because it's a crappy test!
        if (stbi_tga_test_file(f))
            return stbi_tga_load_from_file(f, x, y, comp, req_comp);
        return epuc("unknown image type", "Image not of any known type, or corrupt");
    }
#endif

    unsigned char *stbi_load_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp)
    {
        int i;
        if (stbi_jpeg_test_memory(buffer, len))
            return stbi_jpeg_load_from_memory(buffer, len, x, y, comp, req_comp);
        if (stbi_png_test_memory(buffer, len))
            return stbi_png_load_from_memory(buffer, len, x, y, comp, req_comp);
        if (stbi_bmp_test_memory(buffer, len))
            return stbi_bmp_load_from_memory(buffer, len, x, y, comp, req_comp);
        if (stbi_psd_test_memory(buffer, len))
            return stbi_psd_load_from_memory(buffer, len, x, y, comp, req_comp);
#ifndef STBI_NO_HDR
        if (stbi_hdr_test_memory(buffer, len))
        {
            float *hdr = stbi_hdr_load_from_memory(buffer, len, x, y, comp, req_comp);
            return hdr_to_ldr(hdr, *x, *y, req_comp ? req_comp : *comp);
        }
#endif
        for (i = 0; i < max_loaders; ++i)
            if (loaders[i]->test_memory(buffer, len))
                return loaders[i]->load_from_memory(buffer, len, x, y, comp, req_comp);
        // test tga last because it's a crappy test!
        if (stbi_tga_test_memory(buffer, len))
            return stbi_tga_load_from_memory(buffer, len, x, y, comp, req_comp);
        return epuc("unknown image type", "Image not of any known type, or corrupt");
    }

#ifndef STBI_NO_HDR

#ifndef STBI_NO_STDIO
    float *stbi_loadf(char const *filename, int *x, int *y, int *comp, int req_comp)
    {
        FILE *f = fopen(filename, "rb");
        float *result;
        if (!f)
            return epf("can't fopen", "Unable to open file");
        result = stbi_loadf_from_file(f, x, y, comp, req_comp);
        fclose(f);
        return result;
    }

    float *stbi_loadf_from_file(FILE *f, int *x, int *y, int *comp, int req_comp)
    {
        unsigned char *data;
#ifndef STBI_NO_HDR
        if (stbi_hdr_test_file(f))
            return stbi_hdr_load_from_file(f, x, y, comp, req_comp);
#endif
        data = stbi_load_from_file(f, x, y, comp, req_comp);
        if (data)
            return ldr_to_hdr(data, *x, *y, req_comp ? req_comp : *comp);
        return epf("unknown image type", "Image not of any known type, or corrupt");
    }
#endif

    float *stbi_loadf_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp)
    {
        stbi_uc *data;
#ifndef STBI_NO_HDR
        if (stbi_hdr_test_memory(buffer, len))
            return stbi_hdr_load_from_memory(buffer, len, x, y, comp, req_comp);
#endif
        data = stbi_load_from_memory(buffer, len, x, y, comp, req_comp);
        if (data)
            return ldr_to_hdr(data, *x, *y, req_comp ? req_comp : *comp);
        return epf("unknown image type", "Image not of any known type, or corrupt");
    }
#endif

    // these is-hdr-or-not is defined independent of whether STBI_NO_HDR is
    // defined, for API simplicity; if STBI_NO_HDR is defined, it always
    // reports false!

    int stbi_is_hdr_from_memory(stbi_uc const *buffer, int len)
    {
#ifndef STBI_NO_HDR
        return stbi_hdr_test_memory(buffer, len);
#else
        return 0;
#endif
    }

#ifndef STBI_NO_STDIO
    extern int stbi_is_hdr(char const *filename)
    {
        FILE *f = fopen(filename, "rb");
        int result = 0;
        if (f)
        {
            result = stbi_is_hdr_from_file(f);
            fclose(f);
        }
        return result;
    }

    extern int stbi_is_hdr_from_file(FILE *f)
    {
#ifndef STBI_NO_HDR
        return stbi_hdr_test_file(f);
#else
        return 0;
#endif
    }

#endif

// @TODO: get image dimensions & components without fully decoding
#ifndef STBI_NO_STDIO
    extern int stbi_info(char const *filename, int *x, int *y, int *comp);
    extern int stbi_info_from_file(FILE *f, int *x, int *y, int *comp);
#endif
    extern int stbi_info_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp);

#ifndef STBI_NO_HDR
    static float h2l_gamma_i = 1.0f / 2.2f, h2l_scale_i = 1.0f;
    static float l2h_gamma = 2.2f, l2h_scale = 1.0f;

    void stbi_hdr_to_ldr_gamma(float gamma)
    {
        h2l_gamma_i = 1 / gamma;
    }
    void stbi_hdr_to_ldr_scale(float scale)
    {
        h2l_scale_i = 1 / scale;
    }

    void stbi_ldr_to_hdr_gamma(float gamma)
    {
        l2h_gamma = gamma;
    }
    void stbi_ldr_to_hdr_scale(float scale)
    {
        l2h_scale = scale;
    }
#endif

    //////////////////////////////////////////////////////////////////////////////
    //
    // Common code used by all image loaders
    //

    enum
    {
        SCAN_load = 0,
        SCAN_type,
        SCAN_header,
    };

    typedef struct
    {
        uint32_t img_x, img_y;
        int img_n, img_out_n;

#ifndef STBI_NO_STDIO
        FILE *img_file;
#endif
        uint8_t *img_buffer, *img_buffer_end;
    } stbi;

#ifndef STBI_NO_STDIO
    static void start_file(stbi *s, FILE *f)
    {
        s->img_file = f;
    }
#endif

    static void start_mem(stbi *s, uint8_t const *buffer, int len)
    {
#ifndef STBI_NO_STDIO
        s->img_file = NULL;
#endif
        s->img_buffer = (uint8_t *)buffer;
        s->img_buffer_end = (uint8_t *)buffer + len;
    }

    __forceinline static int get8(stbi *s)
    {
#ifndef STBI_NO_STDIO
        if (s->img_file)
        {
            int c = fgetc(s->img_file);
            return c == EOF ? 0 : c;
        }
#endif
        if (s->img_buffer < s->img_buffer_end)
            return *s->img_buffer++;
        return 0;
    }

    __forceinline static int at_eof(stbi *s)
    {
#ifndef STBI_NO_STDIO
        if (s->img_file)
            return feof(s->img_file);
#endif
        return s->img_buffer >= s->img_buffer_end;
    }

    __forceinline static uint8_t get8u(stbi *s)
    {
        return (uint8_t)get8(s);
    }

    static void skip(stbi *s, int n)
    {
#ifndef STBI_NO_STDIO
        if (s->img_file)
            fseek(s->img_file, n, SEEK_CUR);
        else
#endif
            s->img_buffer += n;
    }

    static int get16(stbi *s)
    {
        int z = get8(s);
        return (z << 8) + get8(s);
    }

    static uint32_t get32(stbi *s)
    {
        uint32_t z = get16(s);
        return (z << 16) + get16(s);
    }

    static int get16le(stbi *s)
    {
        int z = get8(s);
        return z + (get8(s) << 8);
    }

    static uint32_t get32le(stbi *s)
    {
        uint32_t z = get16le(s);
        return z + (get16le(s) << 16);
    }

    static void getn(stbi *s, stbi_uc *buffer, int n)
    {
#ifndef STBI_NO_STDIO
        if (s->img_file)
        {
            size_t nr = fread(buffer, 1, n, s->img_file);
            VOGL_NOTE_UNUSED(nr);
            return;
        }
#endif
        memcpy(buffer, s->img_buffer, n);
        s->img_buffer += n;
    }

    //////////////////////////////////////////////////////////////////////////////
    //
    //  generic converter from built-in img_n to req_comp
    //    individual types do this automatically as much as possible (e.g. jpeg
    //    does all cases internally since it needs to colorspace convert anyway,
    //    and it never has alpha, so very few cases ). png can automatically
    //    interleave an alpha=255 channel, but falls back to this for other cases
    //
    //  assume data buffer is malloced, so stb_malloc a new one and free that one
    //  only failure mode is stb_malloc failing

    static uint8_t compute_y(int r, int g, int b)
    {
        return (uint8_t)(((r * 77) + (g * 150) + (29 * b)) >> 8);
    }

    static unsigned char *convert_format(unsigned char *data, int img_n, int req_comp, uint32_t x, uint32_t y)
    {
        int i, j;
        unsigned char *good;

        if (req_comp == img_n)
            return data;
        assert(req_comp >= 1 && req_comp <= 4);

        good = (unsigned char *)stb_malloc(req_comp * x * y);
        if (good == NULL)
        {
            stb_free(data);
            return epuc("outofmem", "Out of memory");
        }

        for (j = 0; j < (int)y; ++j)
        {
            unsigned char *src = data + j * x * img_n;
            unsigned char *dest = good + j * x * req_comp;

#define COMBO(a, b) ((a) * 8 + (b))
#define CASE(a, b)     \
    case COMBO(a, b) : \
        for (i = x - 1; i >= 0; --i, src += a, dest += b)
            // convert source image with img_n components to one with req_comp components;
            // avoid switch per pixel, so use switch per scanline and massive macros
            switch (COMBO(img_n, req_comp))
            {
                CASE(1, 2) dest[0] = src[0], dest[1] = 255;
                break;
                CASE(1, 3) dest[0] = dest[1] = dest[2] = src[0];
                break;
                CASE(1, 4) dest[0] = dest[1] = dest[2] = src[0], dest[3] = 255;
                break;
                CASE(2, 1) dest[0] = src[0];
                break;
                CASE(2, 3) dest[0] = dest[1] = dest[2] = src[0];
                break;
                CASE(2, 4) dest[0] = dest[1] = dest[2] = src[0], dest[3] = src[1];
                break;
                CASE(3, 4) dest[0] = src[0], dest[1] = src[1], dest[2] = src[2], dest[3] = 255;
                break;
                CASE(3, 1) dest[0] = compute_y(src[0], src[1], src[2]);
                break;
                CASE(3, 2) dest[0] = compute_y(src[0], src[1], src[2]), dest[1] = 255;
                break;
                CASE(4, 1) dest[0] = compute_y(src[0], src[1], src[2]);
                break;
                CASE(4, 2) dest[0] = compute_y(src[0], src[1], src[2]), dest[1] = src[3];
                break;
                CASE(4, 3) dest[0] = src[0], dest[1] = src[1], dest[2] = src[2];
                break;
                default:
                    assert(0);
            }
#undef CASE
        }

        stb_free(data);
        return good;
    }

#ifndef STBI_NO_HDR
    static float *ldr_to_hdr(stbi_uc *data, int x, int y, int comp)
    {
        int i, k, n;
        float *output = (float *)stb_malloc(x * y * comp * sizeof(float));
        if (output == NULL)
        {
            stb_free(data);
            return epf("outofmem", "Out of memory");
        }
        // compute number of non-alpha components
        if (comp & 1)
            n = comp;
        else
            n = comp - 1;
        for (i = 0; i < x * y; ++i)
        {
            for (k = 0; k < n; ++k)
            {
                output[i * comp + k] = (float)pow(data[i * comp + k] / 255.0f, l2h_gamma) * l2h_scale;
            }
            if (k < comp)
                output[i * comp + k] = data[i * comp + k] / 255.0f;
        }
        stb_free(data);
        return output;
    }

#define float2int(x) ((int)(x))
    static stbi_uc *hdr_to_ldr(float *data, int x, int y, int comp)
    {
        int i, k, n;
        stbi_uc *output = (stbi_uc *)stb_malloc(x * y * comp);
        if (output == NULL)
        {
            stb_free(data);
            return epuc("outofmem", "Out of memory");
        }
        // compute number of non-alpha components
        if (comp & 1)
            n = comp;
        else
            n = comp - 1;
        for (i = 0; i < x * y; ++i)
        {
            for (k = 0; k < n; ++k)
            {
                float z = (float)pow(data[i * comp + k] * h2l_scale_i, h2l_gamma_i) * 255 + 0.5f;
                if (z < 0)
                    z = 0;
                if (z > 255)
                    z = 255;
                output[i * comp + k] = float2int(z);
            }
            if (k < comp)
            {
                float z = data[i * comp + k] * 255 + 0.5f;
                if (z < 0)
                    z = 0;
                if (z > 255)
                    z = 255;
                output[i * comp + k] = float2int(z);
            }
        }
        stb_free(data);
        return output;
    }
#endif

//////////////////////////////////////////////////////////////////////////////
//
//  "baseline" JPEG/JFIF decoder (not actually fully baseline implementation)
//
//    simple implementation
//      - channel subsampling of at most 2 in each dimension
//      - doesn't support delayed output of y-dimension
//      - simple interface (only one output format: 8-bit interleaved RGB)
//      - doesn't try to recover corrupt jpegs
//      - doesn't allow partial loading, loading multiple at once
//      - still fast on x86 (copying globals into locals doesn't help x86)
//      - allocates lots of intermediate memory (full size of all components)
//        - non-interleaved case requires this anyway
//        - allows good upsampling (see next)
//    high-quality
//      - upsampled channels are bilinearly interpolated, even across blocks
//      - quality integer IDCT derived from IJG's 'slow'
//    performance
//      - fast huffman; reasonable integer IDCT
//      - uses a lot of intermediate memory, could cache poorly
//      - load http://nothings.org/remote/anemones.jpg 3 times on 2.8Ghz P4
//          stb_jpeg:   1.34 seconds (MSVC6, default release build)
//          stb_jpeg:   1.06 seconds (MSVC6, processor = Pentium Pro)
//          IJL11.dll:  1.08 seconds (compiled by intel)
//          IJG 1998:   0.98 seconds (MSVC6, makefile provided by IJG)
//          IJG 1998:   0.95 seconds (MSVC6, makefile + proc=PPro)

// huffman decoding acceleration
#define FAST_BITS 9 // larger handles more cases; smaller stomps less cache

    typedef struct
    {
        uint8_t fast[1 << FAST_BITS];
        // weirdly, repacking this into AoS is a 10% speed loss, instead of a win
        uint16_t code[256];
        uint8_t values[256];
        uint8_t size[257];
        unsigned int maxcode[18];
        int delta[17]; // old 'firstsymbol' - old 'firstcode'
    } huffman;

    typedef struct
    {
#if STBI_SIMD
        unsigned short dequant2[4][64];
#endif
        stbi s;
        huffman huff_dc[4];
        huffman huff_ac[4];
        uint8_t dequant[4][64];

        // sizes for components, interleaved MCUs
        int img_h_max, img_v_max;
        int img_mcu_x, img_mcu_y;
        int img_mcu_w, img_mcu_h;

        // definition of jpeg image component
        struct
        {
            int id;
            int h, v;
            int tq;
            int hd, ha;
            int dc_pred;

            int x, y, w2, h2;
            uint8_t *data;
            void *raw_data;
            uint8_t *linebuf;
        } img_comp[4];

        uint32_t code_buffer;   // jpeg entropy-coded buffer
        int code_bits;        // number of valid bits
        unsigned char marker; // marker seen while filling entropy buffer
        int nomore;           // flag if we saw a marker so must stop

        int scan_n, order[4];
        int restart_interval, todo;
    } jpeg;

    static int build_huffman(huffman *h, int *count)
    {
        int i, j, k = 0, code;
        // build size list for each symbol (from JPEG spec)
        for (i = 0; i < 16; ++i)
            for (j = 0; j < count[i]; ++j)
                h->size[k++] = (uint8_t)(i + 1);
        h->size[k] = 0;

        // compute actual symbols (from jpeg spec)
        code = 0;
        k = 0;
        for (j = 1; j <= 16; ++j)
        {
            // compute delta to add to code to compute symbol id
            h->delta[j] = k - code;
            if (h->size[k] == j)
            {
                while (h->size[k] == j)
                    h->code[k++] = (uint16_t)(code++);
                if (code - 1 >= (1 << j))
                    return e("bad code lengths", "Corrupt JPEG");
            }
            // compute largest code + 1 for this size, preshifted as needed later
            h->maxcode[j] = code << (16 - j);
            code <<= 1;
        }
        h->maxcode[j] = 0xffffffff;

        // build non-spec acceleration table; 255 is flag for not-accelerated
        memset(h->fast, 255, 1 << FAST_BITS);
        for (i = 0; i < k; ++i)
        {
            int s = h->size[i];
            if (s <= FAST_BITS)
            {
                int c = h->code[i] << (FAST_BITS - s);
                int m = 1 << (FAST_BITS - s);
                for (j = 0; j < m; ++j)
                {
                    h->fast[c + j] = (uint8_t)i;
                }
            }
        }
        return 1;
    }

    static void grow_buffer_unsafe(jpeg *j)
    {
        do
        {
            int b = j->nomore ? 0 : get8(&j->s);
            if (b == 0xff)
            {
                int c = get8(&j->s);
                if (c != 0)
                {
                    j->marker = (unsigned char)c;
                    j->nomore = 1;
                    return;
                }
            }
            j->code_buffer = (j->code_buffer << 8) | b;
            j->code_bits += 8;
        } while (j->code_bits <= 24);
    }

    // (1 << n) - 1
    static uint32_t bmask[17] = { 0, 1, 3, 7, 15, 31, 63, 127, 255, 511, 1023, 2047, 4095, 8191, 16383, 32767, 65535 };

    // decode a jpeg huffman value from the bitstream
    __forceinline static int decode(jpeg *j, huffman *h)
    {
        unsigned int temp;
        int c, k;

        if (j->code_bits < 16)
            grow_buffer_unsafe(j);

        // look at the top FAST_BITS and determine what symbol ID it is,
        // if the code is <= FAST_BITS
        c = (j->code_buffer >> (j->code_bits - FAST_BITS)) & ((1 << FAST_BITS) - 1);
        k = h->fast[c];
        if (k < 255)
        {
            if (h->size[k] > j->code_bits)
                return -1;
            j->code_bits -= h->size[k];
            return h->values[k];
        }

        // naive test is to shift the code_buffer down so k bits are
        // valid, then test against maxcode. To speed this up, we've
        // preshifted maxcode left so that it has (16-k) 0s at the
        // end; in other words, regardless of the number of bits, it
        // wants to be compared against something shifted to have 16;
        // that way we don't need to shift inside the loop.
        if (j->code_bits < 16)
            temp = (j->code_buffer << (16 - j->code_bits)) & 0xffff;
        else
            temp = (j->code_buffer >> (j->code_bits - 16)) & 0xffff;
        for (k = FAST_BITS + 1;; ++k)
            if (temp < h->maxcode[k])
                break;
        if (k == 17)
        {
            // error! code not found
            j->code_bits -= 16;
            return -1;
        }

        if (k > j->code_bits)
            return -1;

        // convert the huffman code to the symbol id
        c = ((j->code_buffer >> (j->code_bits - k)) & bmask[k]) + h->delta[k];
        assert((((j->code_buffer) >> (j->code_bits - h->size[c])) & bmask[h->size[c]]) == h->code[c]);

        // convert the id to a symbol
        j->code_bits -= k;
        return h->values[c];
    }

    // combined JPEG 'receive' and JPEG 'extend', since baseline
    // always extends everything it receives.
    __forceinline static int extend_receive(jpeg *j, int n)
    {
        unsigned int m = 1 << (n - 1);
        unsigned int k;
        if (j->code_bits < n)
            grow_buffer_unsafe(j);
        k = (j->code_buffer >> (j->code_bits - n)) & bmask[n];
        j->code_bits -= n;
        // the following test is probably a random branch that won't
        // predict well. I tried to table accelerate it but failed.
        // maybe it's compiling as a conditional move?
        if (k < m)
            return (-1 << n) + k + 1;
        else
            return k;
    }

    // given a value that's at position X in the zigzag stream,
    // where does it appear in the 8x8 matrix coded as row-major?
    static uint8_t dezigzag[64 + 15] =
        {
            0, 1, 8, 16, 9, 2, 3, 10,
            17, 24, 32, 25, 18, 11, 4, 5,
            12, 19, 26, 33, 40, 48, 41, 34,
            27, 20, 13, 6, 7, 14, 21, 28,
            35, 42, 49, 56, 57, 50, 43, 36,
            29, 22, 15, 23, 30, 37, 44, 51,
            58, 59, 52, 45, 38, 31, 39, 46,
            53, 60, 61, 54, 47, 55, 62, 63,
            // let corrupt input sample past end
            63, 63, 63, 63, 63, 63, 63, 63,
            63, 63, 63, 63, 63, 63, 63
        };

    // decode one 64-entry block--
    static int decode_block(jpeg *j, short data[64], huffman *hdc, huffman *hac, int b)
    {
        int diff, dc, k;
        int t = decode(j, hdc);
        if (t < 0)
            return e("bad huffman code", "Corrupt JPEG");

        // 0 all the ac values now so we can do it 32-bits at a time
        memset(data, 0, 64 * sizeof(data[0]));

        diff = t ? extend_receive(j, t) : 0;
        dc = j->img_comp[b].dc_pred + diff;
        j->img_comp[b].dc_pred = dc;
        data[0] = (short)dc;

        // decode AC components, see JPEG spec
        k = 1;
        do
        {
            int r, s;
            int rs = decode(j, hac);
            if (rs < 0)
                return e("bad huffman code", "Corrupt JPEG");
            s = rs & 15;
            r = rs >> 4;
            if (s == 0)
            {
                if (rs != 0xf0)
                    break; // end block
                k += 16;
            }
            else
            {
                k += r;
                // decode into unzigzag'd location
                data[dezigzag[k++]] = (short)extend_receive(j, s);
            }
        } while (k < 64);
        return 1;
    }

    // take a -128..127 value and clamp it and convert to 0..255
    __forceinline static uint8_t clamp(int x)
    {
        x += 128;
        // trick to use a single test to catch both cases
        if ((unsigned int)x > 255)
        {
            if (x < 0)
                return 0;
            if (x > 255)
                return 255;
        }
        return (uint8_t)x;
    }

#define f2f(x) (int)(((x) * 4096 + 0.5))
#define fsh(x) ((x) << 12)

// derived from jidctint -- DCT_ISLOW
#define IDCT_1D(s0, s1, s2, s3, s4, s5, s6, s7)             \
    int t0, t1, t2, t3, p1, p2, p3, p4, p5, x0, x1, x2, x3; \
    p2 = s2;                                                \
    p3 = s6;                                                \
    p1 = (p2 + p3) * f2f(0.5411961f);                       \
    t2 = p1 + p3 * f2f(-1.847759065f);                      \
    t3 = p1 + p2 * f2f(0.765366865f);                       \
    p2 = s0;                                                \
    p3 = s4;                                                \
    t0 = fsh(p2 + p3);                                      \
    t1 = fsh(p2 - p3);                                      \
    x0 = t0 + t3;                                           \
    x3 = t0 - t3;                                           \
    x1 = t1 + t2;                                           \
    x2 = t1 - t2;                                           \
    t0 = s7;                                                \
    t1 = s5;                                                \
    t2 = s3;                                                \
    t3 = s1;                                                \
    p3 = t0 + t2;                                           \
    p4 = t1 + t3;                                           \
    p1 = t0 + t3;                                           \
    p2 = t1 + t2;                                           \
    p5 = (p3 + p4) * f2f(1.175875602f);                     \
    t0 = t0 * f2f(0.298631336f);                            \
    t1 = t1 * f2f(2.053119869f);                            \
    t2 = t2 * f2f(3.072711026f);                            \
    t3 = t3 * f2f(1.501321110f);                            \
    p1 = p5 + p1 * f2f(-0.899976223f);                      \
    p2 = p5 + p2 * f2f(-2.562915447f);                      \
    p3 = p3 * f2f(-1.961570560f);                           \
    p4 = p4 * f2f(-0.390180644f);                           \
    t3 += p1 + p4;                                          \
    t2 += p2 + p3;                                          \
    t1 += p2 + p4;                                          \
    t0 += p1 + p3;

#if !STBI_SIMD
    // .344 seconds on 3*anemones.jpg
    static void idct_block(uint8_t *out, int out_stride, short data[64], uint8_t *dequantize)
    {
        int i, val[64], *v = val;
        uint8_t *o, *dq = dequantize;
        short *d = data;

        // columns
        for (i = 0; i < 8; ++i, ++d, ++dq, ++v)
        {
            // if all zeroes, shortcut -- this avoids dequantizing 0s and IDCTing
            if (d[8] == 0 && d[16] == 0 && d[24] == 0 && d[32] == 0 && d[40] == 0 && d[48] == 0 && d[56] == 0)
            {
                //    no shortcut                 0     seconds
                //    (1|2|3|4|5|6|7)==0          0     seconds
                //    all separate               -0.047 seconds
                //    1 && 2|3 && 4|5 && 6|7:    -0.047 seconds
                int dcterm = d[0] * dq[0] << 2;
                v[0] = v[8] = v[16] = v[24] = v[32] = v[40] = v[48] = v[56] = dcterm;
            }
            else
            {
                IDCT_1D(d[0] * dq[0], d[8] * dq[8], d[16] * dq[16], d[24] * dq[24],
                        d[32] * dq[32], d[40] * dq[40], d[48] * dq[48], d[56] * dq[56])
                // constants scaled things up by 1<<12; let's bring them back
                // down, but keep 2 extra bits of precision
                x0 += 512;
                x1 += 512;
                x2 += 512;
                x3 += 512;
                v[0] = (x0 + t3) >> 10;
                v[56] = (x0 - t3) >> 10;
                v[8] = (x1 + t2) >> 10;
                v[48] = (x1 - t2) >> 10;
                v[16] = (x2 + t1) >> 10;
                v[40] = (x2 - t1) >> 10;
                v[24] = (x3 + t0) >> 10;
                v[32] = (x3 - t0) >> 10;
            }
        }

        for (i = 0, v = val, o = out; i < 8; ++i, v += 8, o += out_stride)
        {
            // no fast case since the first 1D IDCT spread components out
            IDCT_1D(v[0], v[1], v[2], v[3], v[4], v[5], v[6], v[7])
            // constants scaled things up by 1<<12, plus we had 1<<2 from first
            // loop, plus horizontal and vertical each scale by sqrt(8) so together
            // we've got an extra 1<<3, so 1<<17 total we need to remove.
            x0 += 65536;
            x1 += 65536;
            x2 += 65536;
            x3 += 65536;
            o[0] = clamp((x0 + t3) >> 17);
            o[7] = clamp((x0 - t3) >> 17);
            o[1] = clamp((x1 + t2) >> 17);
            o[6] = clamp((x1 - t2) >> 17);
            o[2] = clamp((x2 + t1) >> 17);
            o[5] = clamp((x2 - t1) >> 17);
            o[3] = clamp((x3 + t0) >> 17);
            o[4] = clamp((x3 - t0) >> 17);
        }
    }
#else
    static void idct_block(uint8_t *out, int out_stride, short data[64], unsigned short *dequantize)
    {
        int i, val[64], *v = val;
        uint8_t *o;
        unsigned short *dq = dequantize;
        short *d = data;

        // columns
        for (i = 0; i < 8; ++i, ++d, ++dq, ++v)
        {
            // if all zeroes, shortcut -- this avoids dequantizing 0s and IDCTing
            if (d[8] == 0 && d[16] == 0 && d[24] == 0 && d[32] == 0 && d[40] == 0 && d[48] == 0 && d[56] == 0)
            {
                //    no shortcut                 0     seconds
                //    (1|2|3|4|5|6|7)==0          0     seconds
                //    all separate               -0.047 seconds
                //    1 && 2|3 && 4|5 && 6|7:    -0.047 seconds
                int dcterm = d[0] * dq[0] << 2;
                v[0] = v[8] = v[16] = v[24] = v[32] = v[40] = v[48] = v[56] = dcterm;
            }
            else
            {
                IDCT_1D(d[0] * dq[0], d[8] * dq[8], d[16] * dq[16], d[24] * dq[24],
                        d[32] * dq[32], d[40] * dq[40], d[48] * dq[48], d[56] * dq[56])
                // constants scaled things up by 1<<12; let's bring them back
                // down, but keep 2 extra bits of precision
                x0 += 512;
                x1 += 512;
                x2 += 512;
                x3 += 512;
                v[0] = (x0 + t3) >> 10;
                v[56] = (x0 - t3) >> 10;
                v[8] = (x1 + t2) >> 10;
                v[48] = (x1 - t2) >> 10;
                v[16] = (x2 + t1) >> 10;
                v[40] = (x2 - t1) >> 10;
                v[24] = (x3 + t0) >> 10;
                v[32] = (x3 - t0) >> 10;
            }
        }

        for (i = 0, v = val, o = out; i < 8; ++i, v += 8, o += out_stride)
        {
            // no fast case since the first 1D IDCT spread components out
            IDCT_1D(v[0], v[1], v[2], v[3], v[4], v[5], v[6], v[7])
            // constants scaled things up by 1<<12, plus we had 1<<2 from first
            // loop, plus horizontal and vertical each scale by sqrt(8) so together
            // we've got an extra 1<<3, so 1<<17 total we need to remove.
            x0 += 65536;
            x1 += 65536;
            x2 += 65536;
            x3 += 65536;
            o[0] = clamp((x0 + t3) >> 17);
            o[7] = clamp((x0 - t3) >> 17);
            o[1] = clamp((x1 + t2) >> 17);
            o[6] = clamp((x1 - t2) >> 17);
            o[2] = clamp((x2 + t1) >> 17);
            o[5] = clamp((x2 - t1) >> 17);
            o[3] = clamp((x3 + t0) >> 17);
            o[4] = clamp((x3 - t0) >> 17);
        }
    }
    static stbi_idct_8x8 stbi_idct_installed = idct_block;

    extern void stbi_install_idct(stbi_idct_8x8 func)
    {
        stbi_idct_installed = func;
    }
#endif

#define MARKER_none 0xff
    // if there's a pending marker from the entropy stream, return that
    // otherwise, fetch from the stream and get a marker. if there's no
    // marker, return 0xff, which is never a valid marker value
    static uint8_t get_marker(jpeg *j)
    {
        uint8_t x;
        if (j->marker != MARKER_none)
        {
            x = j->marker;
            j->marker = MARKER_none;
            return x;
        }
        x = get8u(&j->s);
        if (x != 0xff)
            return MARKER_none;
        while (x == 0xff)
            x = get8u(&j->s);
        return x;
    }

// in each scan, we'll have scan_n components, and the order
// of the components is specified by order[]
#define RESTART(x) ((x) >= 0xd0 && (x) <= 0xd7)

    // after a restart interval, reset the entropy decoder and
    // the dc prediction
    static void reset(jpeg *j)
    {
        j->code_bits = 0;
        j->code_buffer = 0;
        j->nomore = 0;
        j->img_comp[0].dc_pred = j->img_comp[1].dc_pred = j->img_comp[2].dc_pred = 0;
        j->marker = MARKER_none;
        j->todo = j->restart_interval ? j->restart_interval : 0x7fffffff;
        // no more than 1<<31 MCUs if no restart_interal? that's plenty safe,
        // since we don't even allow 1<<30 pixels
    }

    static int parse_entropy_coded_data(jpeg *z)
    {
        reset(z);
        if (z->scan_n == 1)
        {
            int i, j;
#if STBI_SIMD
            __declspec(align(16))
#endif
                short data[64];
            int n = z->order[0];
            // non-interleaved data, we just need to process one block at a time,
            // in trivial scanline order
            // number of blocks to do just depends on how many actual "pixels" this
            // component has, independent of interleaved MCU blocking and such
            int w = (z->img_comp[n].x + 7) >> 3;
            int h = (z->img_comp[n].y + 7) >> 3;
            for (j = 0; j < h; ++j)
            {
                for (i = 0; i < w; ++i)
                {
                    if (!decode_block(z, data, z->huff_dc + z->img_comp[n].hd, z->huff_ac + z->img_comp[n].ha, n))
                        return 0;
#if STBI_SIMD
                    stbi_idct_installed(z->img_comp[n].data + z->img_comp[n].w2 * j * 8 + i * 8, z->img_comp[n].w2, data, z->dequant2[z->img_comp[n].tq]);
#else
                    idct_block(z->img_comp[n].data + z->img_comp[n].w2 * j * 8 + i * 8, z->img_comp[n].w2, data, z->dequant[z->img_comp[n].tq]);
#endif
                    // every data block is an MCU, so countdown the restart interval
                    if (--z->todo <= 0)
                    {
                        if (z->code_bits < 24)
                            grow_buffer_unsafe(z);
                        // if it's NOT a restart, then just bail, so we get corrupt data
                        // rather than no data
                        if (!RESTART(z->marker))
                            return 1;
                        reset(z);
                    }
                }
            }
        }
        else // interleaved!
        {
            int i, j, k, x, y;
            short data[64];
            for (j = 0; j < z->img_mcu_y; ++j)
            {
                for (i = 0; i < z->img_mcu_x; ++i)
                {
                    // scan an interleaved mcu... process scan_n components in order
                    for (k = 0; k < z->scan_n; ++k)
                    {
                        int n = z->order[k];
                        // scan out an mcu's worth of this component; that's just determined
                        // by the basic H and V specified for the component
                        for (y = 0; y < z->img_comp[n].v; ++y)
                        {
                            for (x = 0; x < z->img_comp[n].h; ++x)
                            {
                                int x2 = (i * z->img_comp[n].h + x) * 8;
                                int y2 = (j * z->img_comp[n].v + y) * 8;
                                if (!decode_block(z, data, z->huff_dc + z->img_comp[n].hd, z->huff_ac + z->img_comp[n].ha, n))
                                    return 0;
#if STBI_SIMD
                                stbi_idct_installed(z->img_comp[n].data + z->img_comp[n].w2 * y2 + x2, z->img_comp[n].w2, data, z->dequant2[z->img_comp[n].tq]);
#else
                                idct_block(z->img_comp[n].data + z->img_comp[n].w2 * y2 + x2, z->img_comp[n].w2, data, z->dequant[z->img_comp[n].tq]);
#endif
                            }
                        }
                    }
                    // after all interleaved components, that's an interleaved MCU,
                    // so now count down the restart interval
                    if (--z->todo <= 0)
                    {
                        if (z->code_bits < 24)
                            grow_buffer_unsafe(z);
                        // if it's NOT a restart, then just bail, so we get corrupt data
                        // rather than no data
                        if (!RESTART(z->marker))
                            return 1;
                        reset(z);
                    }
                }
            }
        }
        return 1;
    }

    static int process_marker(jpeg *z, int m)
    {
        int L;
        switch (m)
        {
            case MARKER_none: // no marker found
                return e("expected marker", "Corrupt JPEG");

            case 0xC2: // SOF - progressive
                return e("progressive jpeg", "JPEG format not supported (progressive)");

            case 0xDD: // DRI - specify restart interval
                if (get16(&z->s) != 4)
                    return e("bad DRI len", "Corrupt JPEG");
                z->restart_interval = get16(&z->s);
                return 1;

            case 0xDB: // DQT - define quantization table
                L = get16(&z->s) - 2;
                while (L > 0)
                {
                    int q = get8(&z->s);
                    int p = q >> 4;
                    int t = q & 15, i;
                    if (p != 0)
                        return e("bad DQT type", "Corrupt JPEG");
                    if (t > 3)
                        return e("bad DQT table", "Corrupt JPEG");
                    for (i = 0; i < 64; ++i)
                        z->dequant[t][dezigzag[i]] = get8u(&z->s);
#if STBI_SIMD
                    for (i = 0; i < 64; ++i)
                        z->dequant2[t][i] = z->dequant[t][i];
#endif
                    L -= 65;
                }
                return L == 0;

            case 0xC4: // DHT - define huffman table
                L = get16(&z->s) - 2;
                while (L > 0)
                {
                    uint8_t *v;
                    int sizes[16], i, m2 = 0;
                    int q = get8(&z->s);
                    int tc = q >> 4;
                    int th = q & 15;
                    if (tc > 1 || th > 3)
                        return e("bad DHT header", "Corrupt JPEG");
                    for (i = 0; i < 16; ++i)
                    {
                        sizes[i] = get8(&z->s);
                        m2 += sizes[i];
                    }
                    L -= 17;
                    if (tc == 0)
                    {
                        if (!build_huffman(z->huff_dc + th, sizes))
                            return 0;
                        v = z->huff_dc[th].values;
                    }
                    else
                    {
                        if (!build_huffman(z->huff_ac + th, sizes))
                            return 0;
                        v = z->huff_ac[th].values;
                    }
                    for (i = 0; i < m2; ++i)
                        v[i] = get8u(&z->s);
                    L -= m2;
                }
                return L == 0;
        }
        // check for comment block or APP blocks
        if ((m >= 0xE0 && m <= 0xEF) || m == 0xFE)
        {
            skip(&z->s, get16(&z->s) - 2);
            return 1;
        }
        return 0;
    }

    // after we see SOS
    static int process_scan_header(jpeg *z)
    {
        int i;
        int Ls = get16(&z->s);
        z->scan_n = get8(&z->s);
        if (z->scan_n < 1 || z->scan_n > 4 || z->scan_n > (int)z->s.img_n)
            return e("bad SOS component count", "Corrupt JPEG");
        if (Ls != 6 + 2 * z->scan_n)
            return e("bad SOS len", "Corrupt JPEG");
        for (i = 0; i < z->scan_n; ++i)
        {
            int id = get8(&z->s), which;
            int q = get8(&z->s);
            for (which = 0; which < z->s.img_n; ++which)
                if (z->img_comp[which].id == id)
                    break;
            if (which == z->s.img_n)
                return 0;
            z->img_comp[which].hd = q >> 4;
            if (z->img_comp[which].hd > 3)
                return e("bad DC huff", "Corrupt JPEG");
            z->img_comp[which].ha = q & 15;
            if (z->img_comp[which].ha > 3)
                return e("bad AC huff", "Corrupt JPEG");
            z->order[i] = which;
        }
        if (get8(&z->s) != 0)
            return e("bad SOS", "Corrupt JPEG");
        get8(&z->s); // should be 63, but might be 0
        if (get8(&z->s) != 0)
            return e("bad SOS", "Corrupt JPEG");

        return 1;
    }

    static int process_frame_header(jpeg *z, int scan)
    {
        stbi *s = &z->s;
        int Lf, p, i, q, h_max = 1, v_max = 1, c;
        Lf = get16(s);
        if (Lf < 11)
            return e("bad SOF len", "Corrupt JPEG"); // JPEG
        p = get8(s);
        if (p != 8)
            return e("only 8-bit", "JPEG format not supported: 8-bit only"); // JPEG baseline
        s->img_y = get16(s);
        if (s->img_y == 0)
            return e("no header height", "JPEG format not supported: delayed height"); // Legal, but we don't handle it--but neither does IJG
        s->img_x = get16(s);
        if (s->img_x == 0)
            return e("0 width", "Corrupt JPEG"); // JPEG requires
        c = get8(s);
        if (c != 3 && c != 1)
            return e("bad component count", "Corrupt JPEG"); // JFIF requires
        s->img_n = c;
        for (i = 0; i < c; ++i)
        {
            z->img_comp[i].data = NULL;
            z->img_comp[i].linebuf = NULL;
        }

        if (Lf != 8 + 3 * s->img_n)
            return e("bad SOF len", "Corrupt JPEG");

        for (i = 0; i < s->img_n; ++i)
        {
            z->img_comp[i].id = get8(s);
            if (z->img_comp[i].id != i + 1) // JFIF requires
                if (z->img_comp[i].id != i) // some version of jpegtran outputs non-JFIF-compliant files!
                    return e("bad component ID", "Corrupt JPEG");
            q = get8(s);
            z->img_comp[i].h = (q >> 4);
            if (!z->img_comp[i].h || z->img_comp[i].h > 4)
                return e("bad H", "Corrupt JPEG");
            z->img_comp[i].v = q & 15;
            if (!z->img_comp[i].v || z->img_comp[i].v > 4)
                return e("bad V", "Corrupt JPEG");
            z->img_comp[i].tq = get8(s);
            if (z->img_comp[i].tq > 3)
                return e("bad TQ", "Corrupt JPEG");
        }

        if (scan != SCAN_load)
            return 1;

        if ((1 << 30) / s->img_x / s->img_n < s->img_y)
            return e("too large", "Image too large to decode");

        for (i = 0; i < s->img_n; ++i)
        {
            if (z->img_comp[i].h > h_max)
                h_max = z->img_comp[i].h;
            if (z->img_comp[i].v > v_max)
                v_max = z->img_comp[i].v;
        }

        // compute interleaved mcu info
        z->img_h_max = h_max;
        z->img_v_max = v_max;
        z->img_mcu_w = h_max * 8;
        z->img_mcu_h = v_max * 8;
        z->img_mcu_x = (s->img_x + z->img_mcu_w - 1) / z->img_mcu_w;
        z->img_mcu_y = (s->img_y + z->img_mcu_h - 1) / z->img_mcu_h;

        for (i = 0; i < s->img_n; ++i)
        {
            // number of effective pixels (e.g. for non-interleaved MCU)
            z->img_comp[i].x = (s->img_x * z->img_comp[i].h + h_max - 1) / h_max;
            z->img_comp[i].y = (s->img_y * z->img_comp[i].v + v_max - 1) / v_max;
            // to simplify generation, we'll allocate enough memory to decode
            // the bogus oversized data from using interleaved MCUs and their
            // big blocks (e.g. a 16x16 iMCU on an image of width 33); we won't
            // discard the extra data until colorspace conversion
            z->img_comp[i].w2 = z->img_mcu_x * z->img_comp[i].h * 8;
            z->img_comp[i].h2 = z->img_mcu_y * z->img_comp[i].v * 8;
            z->img_comp[i].raw_data = stb_malloc(z->img_comp[i].w2 * z->img_comp[i].h2 + 15);
            if (z->img_comp[i].raw_data == NULL)
            {
                for (--i; i >= 0; --i)
                {
                    stb_free(z->img_comp[i].raw_data);
                    z->img_comp[i].data = NULL;
                }
                return e("outofmem", "Out of memory");
            }
            // align blocks for installable-idct using mmx/sse
            z->img_comp[i].data = (uint8_t *)(((size_t)z->img_comp[i].raw_data + 15) & ~15);
            z->img_comp[i].linebuf = NULL;
        }

        return 1;
    }

// use comparisons since in some cases we handle more than one case (e.g. SOF)
#define DNL(x) ((x) == 0xdc)
#define SOI(x) ((x) == 0xd8)
#define EOI(x) ((x) == 0xd9)
#define SOF(x) ((x) == 0xc0 || (x) == 0xc1)
#define SOS(x) ((x) == 0xda)

    static int decode_jpeg_header(jpeg *z, int scan)
    {
        int m;
        z->marker = MARKER_none; // initialize cached marker to empty
        m = get_marker(z);
        if (!SOI(m))
            return e("no SOI", "Corrupt JPEG");
        if (scan == SCAN_type)
            return 1;
        m = get_marker(z);
        while (!SOF(m))
        {
            if (!process_marker(z, m))
                return 0;
            m = get_marker(z);
            while (m == MARKER_none)
            {
                // some files have extra padding after their blocks, so ok, we'll scan
                if (at_eof(&z->s))
                    return e("no SOF", "Corrupt JPEG");
                m = get_marker(z);
            }
        }
        if (!process_frame_header(z, scan))
            return 0;
        return 1;
    }

    static int decode_jpeg_image(jpeg *j)
    {
        int m;
        j->restart_interval = 0;
        if (!decode_jpeg_header(j, SCAN_load))
            return 0;
        m = get_marker(j);
        while (!EOI(m))
        {
            if (SOS(m))
            {
                if (!process_scan_header(j))
                    return 0;
                if (!parse_entropy_coded_data(j))
                    return 0;
            }
            else
            {
                if (!process_marker(j, m))
                    return 0;
            }
            m = get_marker(j);
        }
        return 1;
    }

    // static jfif-centered resampling (across block boundaries)

    typedef uint8_t *(*resample_row_func)(uint8_t *out, uint8_t *in0, uint8_t *in1,
                                        int w, int hs);

#define div4(x) ((uint8_t)((x) >> 2))

    static uint8_t *resample_row_1(uint8_t *out, uint8_t *in_near, uint8_t *in_far, int w, int hs)
    {
        VOGL_NOTE_UNUSED(out), VOGL_NOTE_UNUSED(in_far), VOGL_NOTE_UNUSED(w), VOGL_NOTE_UNUSED(hs);
        return in_near;
    }

    static uint8_t *resample_row_v_2(uint8_t *out, uint8_t *in_near, uint8_t *in_far, int w, int hs)
    {
        VOGL_NOTE_UNUSED(hs);
        // need to generate two samples vertically for every one in input
        int i;
        for (i = 0; i < w; ++i)
            out[i] = div4(3 * in_near[i] + in_far[i] + 2);
        return out;
    }

    static uint8_t *resample_row_h_2(uint8_t *out, uint8_t *in_near, uint8_t *in_far, int w, int hs)
    {
        VOGL_NOTE_UNUSED(hs), VOGL_NOTE_UNUSED(in_far);
        // need to generate two samples horizontally for every one in input
        int i;
        uint8_t *input = in_near;
        if (w == 1)
        {
            // if only one sample, can't do any interpolation
            out[0] = out[1] = input[0];
            return out;
        }

        out[0] = input[0];
        out[1] = div4(input[0] * 3 + input[1] + 2);
        for (i = 1; i < w - 1; ++i)
        {
            int n = 3 * input[i] + 2;
            out[i * 2 + 0] = div4(n + input[i - 1]);
            out[i * 2 + 1] = div4(n + input[i + 1]);
        }
        out[i * 2 + 0] = div4(input[w - 2] * 3 + input[w - 1] + 2);
        out[i * 2 + 1] = input[w - 1];
        return out;
    }

#define div16(x) ((uint8_t)((x) >> 4))

    static uint8_t *resample_row_hv_2(uint8_t *out, uint8_t *in_near, uint8_t *in_far, int w, int hs)
    {
        VOGL_NOTE_UNUSED(hs);
        // need to generate 2x2 samples for every one in input
        int i, t0, t1;
        if (w == 1)
        {
            out[0] = out[1] = div4(3 * in_near[0] + in_far[0] + 2);
            return out;
        }

        t1 = 3 * in_near[0] + in_far[0];
        out[0] = div4(t1 + 2);
        for (i = 1; i < w; ++i)
        {
            t0 = t1;
            t1 = 3 * in_near[i] + in_far[i];
            out[i * 2 - 1] = div16(3 * t0 + t1 + 8);
            out[i * 2] = div16(3 * t1 + t0 + 8);
        }
        out[w * 2 - 1] = div4(t1 + 2);
        return out;
    }

    static uint8_t *resample_row_generic(uint8_t *out, uint8_t *in_near, uint8_t *in_far, int w, int hs)
    {
        VOGL_NOTE_UNUSED(in_far);
        // resample with nearest-neighbor
        int i, j;
        for (i = 0; i < w; ++i)
            for (j = 0; j < hs; ++j)
                out[i * hs + j] = in_near[i];
        return out;
    }

#define float2fixed(x) ((int)((x) * 65536 + 0.5))

    // 0.38 seconds on 3*anemones.jpg   (0.25 with processor = Pro)
    // VC6 without processor=Pro is generating multiple LEAs per multiply!
    static void YCbCr_to_RGB_row(uint8_t *out, const uint8_t *y, const uint8_t *pcb, const uint8_t *pcr, int count, int step)
    {
        int i;
        for (i = 0; i < count; ++i)
        {
            int y_fixed = (y[i] << 16) + 32768; // rounding
            int r, g, b;
            int cr = pcr[i] - 128;
            int cb = pcb[i] - 128;
            r = y_fixed + cr * float2fixed(1.40200f);
            g = y_fixed - cr * float2fixed(0.71414f) - cb * float2fixed(0.34414f);
            b = y_fixed + cb * float2fixed(1.77200f);
            r >>= 16;
            g >>= 16;
            b >>= 16;
            if ((unsigned)r > 255)
            {
                if (r < 0)
                    r = 0;
                else
                    r = 255;
            }
            if ((unsigned)g > 255)
            {
                if (g < 0)
                    g = 0;
                else
                    g = 255;
            }
            if ((unsigned)b > 255)
            {
                if (b < 0)
                    b = 0;
                else
                    b = 255;
            }
            out[0] = (uint8_t)r;
            out[1] = (uint8_t)g;
            out[2] = (uint8_t)b;
            out[3] = 255;
            out += step;
        }
    }

#if STBI_SIMD
    static stbi_YCbCr_to_RGB_run stbi_YCbCr_installed = YCbCr_to_RGB_row;

    void stbi_install_YCbCr_to_RGB(stbi_YCbCr_to_RGB_run func)
    {
        stbi_YCbCr_installed = func;
    }
#endif

    // clean up the temporary component buffers
    static void cleanup_jpeg(jpeg *j)
    {
        int i;
        for (i = 0; i < j->s.img_n; ++i)
        {
            if (j->img_comp[i].data)
            {
                stb_free(j->img_comp[i].raw_data);
                j->img_comp[i].data = NULL;
            }
            if (j->img_comp[i].linebuf)
            {
                stb_free(j->img_comp[i].linebuf);
                j->img_comp[i].linebuf = NULL;
            }
        }
    }

    typedef struct
    {
        resample_row_func resample;
        uint8_t *line0, *line1;
        int hs, vs;  // expansion factor in each axis
        int w_lores; // horizontal pixels pre-expansion
        int ystep;   // how far through vertical expansion we are
        int ypos;    // which pre-expansion row we're on
    } stbi_resample;

    static uint8_t *load_jpeg_image(jpeg *z, int *out_x, int *out_y, int *comp, int req_comp)
    {
        int n, decode_n;
        // validate req_comp
        if (req_comp < 0 || req_comp > 4)
            return epuc("bad req_comp", "Internal error");
        z->s.img_n = 0;

        // load a jpeg image from whichever source
        if (!decode_jpeg_image(z))
        {
            cleanup_jpeg(z);
            return NULL;
        }

        // determine actual number of components to generate
        n = req_comp ? req_comp : z->s.img_n;

        if (z->s.img_n == 3 && n < 3)
            decode_n = 1;
        else
            decode_n = z->s.img_n;

        // resample and color-convert
        {
            int k;
            uint32_t i, j;
            uint8_t *output;
            uint8_t *coutput[4];

            stbi_resample res_comp[4];

            for (k = 0; k < decode_n; ++k)
            {
                stbi_resample *r = &res_comp[k];

                // allocate line buffer big enough for upsampling off the edges
                // with upsample factor of 4
                z->img_comp[k].linebuf = (uint8_t *)stb_malloc(z->s.img_x + 3);
                if (!z->img_comp[k].linebuf)
                {
                    cleanup_jpeg(z);
                    return epuc("outofmem", "Out of memory");
                }

                r->hs = z->img_h_max / z->img_comp[k].h;
                r->vs = z->img_v_max / z->img_comp[k].v;
                r->ystep = r->vs >> 1;
                r->w_lores = (z->s.img_x + r->hs - 1) / r->hs;
                r->ypos = 0;
                r->line0 = r->line1 = z->img_comp[k].data;

                if (r->hs == 1 && r->vs == 1)
                    r->resample = resample_row_1;
                else if (r->hs == 1 && r->vs == 2)
                    r->resample = resample_row_v_2;
                else if (r->hs == 2 && r->vs == 1)
                    r->resample = resample_row_h_2;
                else if (r->hs == 2 && r->vs == 2)
                    r->resample = resample_row_hv_2;
                else
                    r->resample = resample_row_generic;
            }

            // can't error after this so, this is safe
            output = (uint8_t *)stb_malloc(n * z->s.img_x * z->s.img_y + 1);
            if (!output)
            {
                cleanup_jpeg(z);
                return epuc("outofmem", "Out of memory");
            }

            // now go ahead and resample
            for (j = 0; j < z->s.img_y; ++j)
            {
                uint8_t *out = output + n * z->s.img_x * j;
                for (k = 0; k < decode_n; ++k)
                {
                    stbi_resample *r = &res_comp[k];
                    int y_bot = r->ystep >= (r->vs >> 1);
                    coutput[k] = r->resample(z->img_comp[k].linebuf,
                                             y_bot ? r->line1 : r->line0,
                                             y_bot ? r->line0 : r->line1,
                                             r->w_lores, r->hs);
                    if (++r->ystep >= r->vs)
                    {
                        r->ystep = 0;
                        r->line0 = r->line1;
                        if (++r->ypos < z->img_comp[k].y)
                            r->line1 += z->img_comp[k].w2;
                    }
                }
                if (n >= 3)
                {
                    uint8_t *y = coutput[0];
                    if (z->s.img_n == 3)
                    {
#if STBI_SIMD
                        stbi_YCbCr_installed(out, y, coutput[1], coutput[2], z->s.img_x, n);
#else
                        YCbCr_to_RGB_row(out, y, coutput[1], coutput[2], z->s.img_x, n);
#endif
                    }
                    else
                        for (i = 0; i < z->s.img_x; ++i)
                        {
                            out[0] = out[1] = out[2] = y[i];
                            out[3] = 255; // not used if n==3
                            out += n;
                        }
                }
                else
                {
                    uint8_t *y = coutput[0];
                    if (n == 1)
                        for (i = 0; i < z->s.img_x; ++i)
                            out[i] = y[i];
                    else
                        for (i = 0; i < z->s.img_x; ++i)
                            *out++ = y[i], *out++ = 255;
                }
            }
            cleanup_jpeg(z);
            *out_x = z->s.img_x;
            *out_y = z->s.img_y;
            if (comp)
                *comp = z->s.img_n; // report original components, not output
            return output;
        }
    }

#ifndef STBI_NO_STDIO
    unsigned char *stbi_jpeg_load_from_file(FILE *f, int *x, int *y, int *comp, int req_comp)
    {
        jpeg j;
        start_file(&j.s, f);
        return load_jpeg_image(&j, x, y, comp, req_comp);
    }

    unsigned char *stbi_jpeg_load(char const *filename, int *x, int *y, int *comp, int req_comp)
    {
        unsigned char *data;
        FILE *f = fopen(filename, "rb");
        if (!f)
            return NULL;
        data = stbi_jpeg_load_from_file(f, x, y, comp, req_comp);
        fclose(f);
        return data;
    }
#endif

    unsigned char *stbi_jpeg_load_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp)
    {
        jpeg j;
        start_mem(&j.s, buffer, len);
        return load_jpeg_image(&j, x, y, comp, req_comp);
    }

#ifndef STBI_NO_STDIO
    int stbi_jpeg_test_file(FILE *f)
    {
        int n, r;
        jpeg j;
        n = (int)ftell(f);
        start_file(&j.s, f);
        r = decode_jpeg_header(&j, SCAN_type);
        fseek(f, n, SEEK_SET);
        return r;
    }
#endif

    int stbi_jpeg_test_memory(stbi_uc const *buffer, int len)
    {
        jpeg j;
        start_mem(&j.s, buffer, len);
        return decode_jpeg_header(&j, SCAN_type);
    }

// @TODO:
#ifndef STBI_NO_STDIO
    extern int stbi_jpeg_info(char const *filename, int *x, int *y, int *comp);
    extern int stbi_jpeg_info_from_file(FILE *f, int *x, int *y, int *comp);
#endif
    extern int stbi_jpeg_info_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp);

// public domain zlib decode    v0.2  Sean Barrett 2006-11-18
//    simple implementation
//      - all input must be provided in an upfront buffer
//      - all output is written to a single output buffer (can stb_malloc/stb_realloc)
//    performance
//      - fast huffman

// fast-way is faster to check than jpeg huffman, but slow way is slower
#define ZFAST_BITS 9 // accelerate all cases in default tables
#define ZFAST_MASK ((1 << ZFAST_BITS) - 1)

    // zlib-style huffman encoding
    // (jpegs packs from left, zlib from right, so can't share code)
    typedef struct
    {
        uint16_t fast[1 << ZFAST_BITS];
        uint16_t firstcode[16];
        int maxcode[17];
        uint16_t firstsymbol[16];
        uint8_t size[288];
        uint16_t value[288];
    } zhuffman;

    __forceinline static int bitreverse16(int n)
    {
        n = ((n & 0xAAAA) >> 1) | ((n & 0x5555) << 1);
        n = ((n & 0xCCCC) >> 2) | ((n & 0x3333) << 2);
        n = ((n & 0xF0F0) >> 4) | ((n & 0x0F0F) << 4);
        n = ((n & 0xFF00) >> 8) | ((n & 0x00FF) << 8);
        return n;
    }

    __forceinline static int bit_reverse(int v, int bits)
    {
        assert(bits <= 16);
        // to bit reverse n bits, reverse 16 and shift
        // e.g. 11 bits, bit reverse and shift away 5
        return bitreverse16(v) >> (16 - bits);
    }

    static int zbuild_huffman(zhuffman *z, uint8_t *sizelist, int num)
    {
        int i, k = 0;
        int code, next_code[16], sizes[17];

        // DEFLATE spec for generating codes
        memset(sizes, 0, sizeof(sizes));
        memset(z->fast, 255, sizeof(z->fast));
        for (i = 0; i < num; ++i)
            ++sizes[sizelist[i]];
        sizes[0] = 0;
        for (i = 1; i < 16; ++i)
            assert(sizes[i] <= (1 << i));
        code = 0;
        for (i = 1; i < 16; ++i)
        {
            next_code[i] = code;
            z->firstcode[i] = (uint16_t)code;
            z->firstsymbol[i] = (uint16_t)k;
            code = (code + sizes[i]);
            if (sizes[i])
                if (code - 1 >= (1 << i))
                    return e("bad codelengths", "Corrupt JPEG");
            z->maxcode[i] = code << (16 - i); // preshift for inner loop
            code <<= 1;
            k += sizes[i];
        }
        z->maxcode[16] = 0x10000; // sentinel
        for (i = 0; i < num; ++i)
        {
            int s = sizelist[i];
            if (s)
            {
                int c = next_code[s] - z->firstcode[s] + z->firstsymbol[s];
                z->size[c] = (uint8_t)s;
                z->value[c] = (uint16_t)i;
                if (s <= ZFAST_BITS)
                {
                    k = bit_reverse(next_code[s], s);
                    while (k < (1 << ZFAST_BITS))
                    {
                        z->fast[k] = (uint16_t)c;
                        k += (1 << s);
                    }
                }
                ++next_code[s];
            }
        }
        return 1;
    }

    // zlib-from-memory implementation for PNG reading
    //    because PNG allows splitting the zlib stream arbitrarily,
    //    and it's annoying structurally to have PNG call ZLIB call PNG,
    //    we require PNG read all the IDATs and combine them into a single
    //    memory buffer

    typedef struct
    {
        uint8_t *zbuffer, *zbuffer_end;
        int num_bits;
        uint32_t code_buffer;

        char *zout;
        char *zout_start;
        char *zout_end;
        int z_expandable;

        zhuffman z_length, z_distance;
    } zbuf;

    __forceinline static int zget8(zbuf *z)
    {
        if (z->zbuffer >= z->zbuffer_end)
            return 0;
        return *z->zbuffer++;
    }

    static void fill_bits(zbuf *z)
    {
        do
        {
            assert(z->code_buffer < (1U << z->num_bits));
            z->code_buffer |= zget8(z) << z->num_bits;
            z->num_bits += 8;
        } while (z->num_bits <= 24);
    }

    __forceinline static unsigned int zreceive(zbuf *z, int n)
    {
        unsigned int k;
        if (z->num_bits < n)
            fill_bits(z);
        k = z->code_buffer & ((1 << n) - 1);
        z->code_buffer >>= n;
        z->num_bits -= n;
        return k;
    }

    __forceinline static int zhuffman_decode(zbuf *a, zhuffman *z)
    {
        int b, s, k;
        if (a->num_bits < 16)
            fill_bits(a);
        b = z->fast[a->code_buffer & ZFAST_MASK];
        if (b < 0xffff)
        {
            s = z->size[b];
            a->code_buffer >>= s;
            a->num_bits -= s;
            return z->value[b];
        }

        // not resolved by fast table, so compute it the slow way
        // use jpeg approach, which requires MSbits at top
        k = bit_reverse(a->code_buffer, 16);
        for (s = ZFAST_BITS + 1;; ++s)
            if (k < z->maxcode[s])
                break;
        if (s == 16)
            return -1; // invalid code!
        // code size is s, so:
        b = (k >> (16 - s)) - z->firstcode[s] + z->firstsymbol[s];
        assert(z->size[b] == s);
        a->code_buffer >>= s;
        a->num_bits -= s;
        return z->value[b];
    }

    static int expand(zbuf *z, int n) // need to make room for n bytes
    {
        char *q;
        int cur, limit;
        if (!z->z_expandable)
            return e("output buffer limit", "Corrupt PNG");
        cur = (int)(z->zout - z->zout_start);
        limit = (int)(z->zout_end - z->zout_start);
        while (cur + n > limit)
            limit *= 2;
        q = (char *)stb_realloc(z->zout_start, limit);
        if (q == NULL)
            return e("outofmem", "Out of memory");
        z->zout_start = q;
        z->zout = q + cur;
        z->zout_end = q + limit;
        return 1;
    }

    static int length_base[31] =
        {
            3, 4, 5, 6, 7, 8, 9, 10, 11, 13,
            15, 17, 19, 23, 27, 31, 35, 43, 51, 59,
            67, 83, 99, 115, 131, 163, 195, 227, 258, 0, 0
        };

    static int length_extra[31] =
        { 0, 0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 0, 0, 0 };

    static int dist_base[32] = { 1, 2, 3, 4, 5, 7, 9, 13, 17, 25, 33, 49, 65, 97, 129, 193,
                                 257, 385, 513, 769, 1025, 1537, 2049, 3073, 4097, 6145, 8193, 12289, 16385, 24577, 0, 0 };

    static int dist_extra[32] =
        { 0, 0, 0, 0, 1, 1, 2, 2, 3, 3, 4, 4, 5, 5, 6, 6, 7, 7, 8, 8, 9, 9, 10, 10, 11, 11, 12, 12, 13, 13 };

    static int parse_huffman_block(zbuf *a)
    {
        for (;;)
        {
            int z = zhuffman_decode(a, &a->z_length);
            if (z < 256)
            {
                if (z < 0)
                    return e("bad huffman code", "Corrupt PNG"); // error in huffman codes
                if (a->zout >= a->zout_end)
                    if (!expand(a, 1))
                        return 0;
                *a->zout++ = (char)z;
            }
            else
            {
                uint8_t *p;
                int len, dist;
                if (z == 256)
                    return 1;
                z -= 257;
                len = length_base[z];
                if (length_extra[z])
                    len += zreceive(a, length_extra[z]);
                z = zhuffman_decode(a, &a->z_distance);
                if (z < 0)
                    return e("bad huffman code", "Corrupt PNG");
                dist = dist_base[z];
                if (dist_extra[z])
                    dist += zreceive(a, dist_extra[z]);
                if (a->zout - a->zout_start < dist)
                    return e("bad dist", "Corrupt PNG");
                if (a->zout + len > a->zout_end)
                    if (!expand(a, len))
                        return 0;
                p = (uint8_t *)(a->zout - dist);
                while (len--)
                    *a->zout++ = *p++;
            }
        }
    }

    static int compute_huffman_codes(zbuf *a)
    {
        static uint8_t length_dezigzag[19] = { 16, 17, 18, 0, 8, 7, 9, 6, 10, 5, 11, 4, 12, 3, 13, 2, 14, 1, 15 };
        zhuffman z_codelength;
        uint8_t lencodes[286 + 32 + 137]; //padding for maximum single op
        uint8_t codelength_sizes[19];
        int i, n;

        int hlit = zreceive(a, 5) + 257;
        int hdist = zreceive(a, 5) + 1;
        int hclen = zreceive(a, 4) + 4;

        memset(codelength_sizes, 0, sizeof(codelength_sizes));
        for (i = 0; i < hclen; ++i)
        {
            int s = zreceive(a, 3);
            codelength_sizes[length_dezigzag[i]] = (uint8_t)s;
        }
        if (!zbuild_huffman(&z_codelength, codelength_sizes, 19))
            return 0;

        n = 0;
        while (n < hlit + hdist)
        {
            int c = zhuffman_decode(a, &z_codelength);
            assert(c >= 0 && c < 19);
            if (c < 16)
                lencodes[n++] = (uint8_t)c;
            else if (c == 16)
            {
                c = zreceive(a, 2) + 3;
                memset(lencodes + n, lencodes[n - 1], c);
                n += c;
            }
            else if (c == 17)
            {
                c = zreceive(a, 3) + 3;
                memset(lencodes + n, 0, c);
                n += c;
            }
            else
            {
                assert(c == 18);
                c = zreceive(a, 7) + 11;
                memset(lencodes + n, 0, c);
                n += c;
            }
        }
        if (n != hlit + hdist)
            return e("bad codelengths", "Corrupt PNG");
        if (!zbuild_huffman(&a->z_length, lencodes, hlit))
            return 0;
        if (!zbuild_huffman(&a->z_distance, lencodes + hlit, hdist))
            return 0;
        return 1;
    }

    static int parse_uncompressed_block(zbuf *a)
    {
        uint8_t header[4];
        int len, nlen, k;
        if (a->num_bits & 7)
            zreceive(a, a->num_bits & 7); // discard
        // drain the bit-packed data into header
        k = 0;
        while (a->num_bits > 0)
        {
            header[k++] = (uint8_t)(a->code_buffer & 255); // wtf this warns?
            a->code_buffer >>= 8;
            a->num_bits -= 8;
        }
        assert(a->num_bits == 0);
        // now fill header the normal way
        while (k < 4)
            header[k++] = (uint8_t)zget8(a);
        len = header[1] * 256 + header[0];
        nlen = header[3] * 256 + header[2];
        if (nlen != (len ^ 0xffff))
            return e("zlib corrupt", "Corrupt PNG");
        if (a->zbuffer + len > a->zbuffer_end)
            return e("read past buffer", "Corrupt PNG");
        if (a->zout + len > a->zout_end)
            if (!expand(a, len))
                return 0;
        memcpy(a->zout, a->zbuffer, len);
        a->zbuffer += len;
        a->zout += len;
        return 1;
    }

    static int parse_zlib_header(zbuf *a)
    {
        int cmf = zget8(a);
        int cm = cmf & 15;
        /* int cinfo = cmf >> 4; */
        int flg = zget8(a);
        if ((cmf * 256 + flg) % 31 != 0)
            return e("bad zlib header", "Corrupt PNG"); // zlib spec
        if (flg & 32)
            return e("no preset dict", "Corrupt PNG"); // preset dictionary not allowed in png
        if (cm != 8)
            return e("bad compression", "Corrupt PNG"); // DEFLATE required for png
        // window = 1 << (8 + cinfo)... but who cares, we fully buffer output
        return 1;
    }

    // @TODO: should statically initialize these for optimal thread safety
    static uint8_t default_length[288], default_distance[32];
    static void init_defaults(void)
    {
        int i; // use <= to match clearly with spec
        for (i = 0; i <= 143; ++i)
            default_length[i] = 8;
        for (; i <= 255; ++i)
            default_length[i] = 9;
        for (; i <= 279; ++i)
            default_length[i] = 7;
        for (; i <= 287; ++i)
            default_length[i] = 8;

        for (i = 0; i <= 31; ++i)
            default_distance[i] = 5;
    }

    int stbi_png_partial; // a quick hack to only allow decoding some of a PNG... I should implement real streaming support instead
    static int parse_zlib(zbuf *a, int parse_header)
    {
        int final, type;
        if (parse_header)
            if (!parse_zlib_header(a))
                return 0;
        a->num_bits = 0;
        a->code_buffer = 0;
        do
        {
            final = zreceive(a, 1);
            type = zreceive(a, 2);
            if (type == 0)
            {
                if (!parse_uncompressed_block(a))
                    return 0;
            }
            else if (type == 3)
            {
                return 0;
            }
            else
            {
                if (type == 1)
                {
                    // use fixed code lengths
                    if (!default_distance[31])
                        init_defaults();
                    if (!zbuild_huffman(&a->z_length, default_length, 288))
                        return 0;
                    if (!zbuild_huffman(&a->z_distance, default_distance, 32))
                        return 0;
                }
                else
                {
                    if (!compute_huffman_codes(a))
                        return 0;
                }
                if (!parse_huffman_block(a))
                    return 0;
            }
            if (stbi_png_partial && a->zout - a->zout_start > 65536)
                break;
        } while (!final);
        return 1;
    }

    static int do_zlib(zbuf *a, char *obuf, int olen, int exp, int parse_header)
    {
        a->zout_start = obuf;
        a->zout = obuf;
        a->zout_end = obuf + olen;
        a->z_expandable = exp;

        return parse_zlib(a, parse_header);
    }

    char *stbi_zlib_decode_malloc_guesssize(const char *buffer, int len, int initial_size, int *outlen)
    {
        zbuf a;
        char *p = (char *)stb_malloc(initial_size);
        if (p == NULL)
            return NULL;
        a.zbuffer = (uint8_t *)buffer;
        a.zbuffer_end = (uint8_t *)buffer + len;
        if (do_zlib(&a, p, initial_size, 1, 1))
        {
            if (outlen)
                *outlen = (int)(a.zout - a.zout_start);
            return a.zout_start;
        }
        else
        {
            stb_free(a.zout_start);
            return NULL;
        }
    }

    char *stbi_zlib_decode_malloc(char const *buffer, int len, int *outlen)
    {
        return stbi_zlib_decode_malloc_guesssize(buffer, len, 16384, outlen);
    }

    int stbi_zlib_decode_buffer(char *obuffer, int olen, char const *ibuffer, int ilen)
    {
        zbuf a;
        a.zbuffer = (uint8_t *)ibuffer;
        a.zbuffer_end = (uint8_t *)ibuffer + ilen;
        if (do_zlib(&a, obuffer, olen, 0, 1))
            return (int)(a.zout - a.zout_start);
        else
            return -1;
    }

    char *stbi_zlib_decode_noheader_malloc(char const *buffer, int len, int *outlen)
    {
        zbuf a;
        char *p = (char *)stb_malloc(16384);
        if (p == NULL)
            return NULL;
        a.zbuffer = (uint8_t *)buffer;
        a.zbuffer_end = (uint8_t *)buffer + len;
        if (do_zlib(&a, p, 16384, 1, 0))
        {
            if (outlen)
                *outlen = (int)(a.zout - a.zout_start);
            return a.zout_start;
        }
        else
        {
            stb_free(a.zout_start);
            return NULL;
        }
    }

    int stbi_zlib_decode_noheader_buffer(char *obuffer, int olen, const char *ibuffer, int ilen)
    {
        zbuf a;
        a.zbuffer = (uint8_t *)ibuffer;
        a.zbuffer_end = (uint8_t *)ibuffer + ilen;
        if (do_zlib(&a, obuffer, olen, 0, 0))
            return (int)(a.zout - a.zout_start);
        else
            return -1;
    }

    // public domain "baseline" PNG decoder   v0.10  Sean Barrett 2006-11-18
    //    simple implementation
    //      - only 8-bit samples
    //      - no CRC checking
    //      - allocates lots of intermediate memory
    //        - avoids problem of streaming data between subsystems
    //        - avoids explicit window management
    //    performance
    //      - uses stb_zlib, a PD zlib implementation with fast huffman decoding

    typedef struct
    {
        uint32_t length;
        uint32_t type;
    } chunk;

#define PNG_TYPE(a, b, c, d) (((a) << 24) + ((b) << 16) + ((c) << 8) + (d))

    static chunk get_chunk_header(stbi *s)
    {
        chunk c;
        c.length = get32(s);
        c.type = get32(s);
        return c;
    }

    static int check_png_header(stbi *s)
    {
        static uint8_t png_sig[8] = { 137, 80, 78, 71, 13, 10, 26, 10 };
        int i;
        for (i = 0; i < 8; ++i)
            if (get8(s) != png_sig[i])
                return e("bad png sig", "Not a PNG");
        return 1;
    }

    typedef struct
    {
        stbi s;
        uint8_t *idata, *expanded, *out;
    } png;

    enum
    {
        F_none = 0,
        F_sub = 1,
        F_up = 2,
        F_avg = 3,
        F_paeth = 4,
        F_avg_first,
        F_paeth_first,
    };

    static uint8_t first_row_filter[5] =
        {
            F_none, F_sub, F_none, F_avg_first, F_paeth_first
        };

    static int paeth(int a, int b, int c)
    {
        int p = a + b - c;
        int pa = abs(p - a);
        int pb = abs(p - b);
        int pc = abs(p - c);
        if (pa <= pb && pa <= pc)
            return a;
        if (pb <= pc)
            return b;
        return c;
    }

    // create the png data from post-deflated data
    static int create_png_image_raw(png *a, uint8_t *raw, uint32_t raw_len, int out_n, uint32_t x, uint32_t y)
    {
        stbi *s = &a->s;
        uint32_t i, j, stride = x * out_n;
        int k;
        int img_n = s->img_n; // copy it into a local for later
        assert(out_n == s->img_n || out_n == s->img_n + 1);
        if (stbi_png_partial)
            y = 1;
        a->out = (uint8_t *)stb_malloc(x * y * out_n);
        if (!a->out)
            return e("outofmem", "Out of memory");
        if (!stbi_png_partial)
        {
            if ((s->img_x == x) && (s->img_y == y))
            {
                if (raw_len != (img_n * x + 1) * y)
                    return e("not enough pixels", "Corrupt PNG");
            }
            else // interlaced:
            {
                if (raw_len < (img_n * x + 1) * y)
                    return e("not enough pixels", "Corrupt PNG");
            }
        }
        for (j = 0; j < y; ++j)
        {
            uint8_t *cur = a->out + stride * j;
            uint8_t *prior = cur - stride;
            int filter = *raw++;
            if (filter > 4)
                return e("invalid filter", "Corrupt PNG");
            // if first row, use special filter that doesn't sample previous row
            if (j == 0)
                filter = first_row_filter[filter];
            // handle first pixel explicitly
            for (k = 0; k < img_n; ++k)
            {
                switch (filter)
                {
                    case F_none:
                        cur[k] = raw[k];
                        break;
                    case F_sub:
                        cur[k] = raw[k];
                        break;
                    case F_up:
                        cur[k] = raw[k] + prior[k];
                        break;
                    case F_avg:
                        cur[k] = raw[k] + (prior[k] >> 1);
                        break;
                    case F_paeth:
                        cur[k] = (uint8_t)(raw[k] + paeth(0, prior[k], 0));
                        break;
                    case F_avg_first:
                        cur[k] = raw[k];
                        break;
                    case F_paeth_first:
                        cur[k] = raw[k];
                        break;
                }
            }
            if (img_n != out_n)
                cur[img_n] = 255;
            raw += img_n;
            cur += out_n;
            prior += out_n;
            // this is a little gross, so that we don't switch per-pixel or per-component
            if (img_n == out_n)
            {
#define CASE(f)                                                                  \
    case f:                                                                      \
        for (i = x - 1; i >= 1; --i, raw += img_n, cur += img_n, prior += img_n) \
            for (k = 0; k < img_n; ++k)
                switch (filter)
                {
                    CASE(F_none) cur[k] = raw[k];
                    break;
                    CASE(F_sub) cur[k] = raw[k] + cur[k - img_n];
                    break;
                    CASE(F_up) cur[k] = raw[k] + prior[k];
                    break;
                    CASE(F_avg) cur[k] = raw[k] + ((prior[k] + cur[k - img_n]) >> 1);
                    break;
                    CASE(F_paeth) cur[k] = (uint8_t)(raw[k] + paeth(cur[k - img_n], prior[k], prior[k - img_n]));
                    break;
                    CASE(F_avg_first) cur[k] = raw[k] + (cur[k - img_n] >> 1);
                    break;
                    CASE(F_paeth_first) cur[k] = (uint8_t)(raw[k] + paeth(cur[k - img_n], 0, 0));
                    break;
                }
#undef CASE
            }
            else
            {
                assert(img_n + 1 == out_n);
#define CASE(f)                                                                                    \
    case f:                                                                                        \
        for (i = x - 1; i >= 1; --i, cur[img_n] = 255, raw += img_n, cur += out_n, prior += out_n) \
            for (k = 0; k < img_n; ++k)
                switch (filter)
                {
                    CASE(F_none) cur[k] = raw[k];
                    break;
                    CASE(F_sub) cur[k] = raw[k] + cur[k - out_n];
                    break;
                    CASE(F_up) cur[k] = raw[k] + prior[k];
                    break;
                    CASE(F_avg) cur[k] = raw[k] + ((prior[k] + cur[k - out_n]) >> 1);
                    break;
                    CASE(F_paeth) cur[k] = (uint8_t)(raw[k] + paeth(cur[k - out_n], prior[k], prior[k - out_n]));
                    break;
                    CASE(F_avg_first) cur[k] = raw[k] + (cur[k - out_n] >> 1);
                    break;
                    CASE(F_paeth_first) cur[k] = (uint8_t)(raw[k] + paeth(cur[k - out_n], 0, 0));
                    break;
                }
#undef CASE
            }
        }
        return 1;
    }

    static int create_png_image(png *a, uint8_t *raw, uint32_t raw_len, int out_n, int interlaced)
    {
        uint8_t *final;
        int p;
        int save;
        if (!interlaced)
            return create_png_image_raw(a, raw, raw_len, out_n, a->s.img_x, a->s.img_y);
        save = stbi_png_partial;
        stbi_png_partial = 0;

        // de-interlacing
        final = (uint8_t *)stb_malloc(a->s.img_x * a->s.img_y * out_n);
        for (p = 0; p < 7; ++p)
        {
            int xorig[] = { 0, 4, 0, 2, 0, 1, 0 };
            int yorig[] = { 0, 0, 4, 0, 2, 0, 1 };
            int xspc[] = { 8, 8, 4, 4, 2, 2, 1 };
            int yspc[] = { 8, 8, 8, 4, 4, 2, 2 };
            int i, j, x, y;
            // pass1_x[4] = 0, pass1_x[5] = 1, pass1_x[12] = 1
            x = (a->s.img_x - xorig[p] + xspc[p] - 1) / xspc[p];
            y = (a->s.img_y - yorig[p] + yspc[p] - 1) / yspc[p];
            if (x && y)
            {
                if (!create_png_image_raw(a, raw, raw_len, out_n, x, y))
                {
                    stb_free(final);
                    return 0;
                }
                for (j = 0; j < y; ++j)
                    for (i = 0; i < x; ++i)
                        memcpy(final + (j * yspc[p] + yorig[p]) * a->s.img_x * out_n + (i * xspc[p] + xorig[p]) * out_n,
                               a->out + (j * x + i) * out_n, out_n);
                stb_free(a->out);
                raw += (x * out_n + 1) * y;
                raw_len -= (x * out_n + 1) * y;
            }
        }
        a->out = final;

        stbi_png_partial = save;
        return 1;
    }

    static int compute_transparency(png *z, uint8_t tc[3], int out_n)
    {
        stbi *s = &z->s;
        uint32_t i, pixel_count = s->img_x * s->img_y;
        uint8_t *p = z->out;

        // compute color-based transparency, assuming we've
        // already got 255 as the alpha value in the output
        assert(out_n == 2 || out_n == 4);

        if (out_n == 2)
        {
            for (i = 0; i < pixel_count; ++i)
            {
                p[1] = (p[0] == tc[0] ? 0 : 255);
                p += 2;
            }
        }
        else
        {
            for (i = 0; i < pixel_count; ++i)
            {
                if (p[0] == tc[0] && p[1] == tc[1] && p[2] == tc[2])
                    p[3] = 0;
                p += 4;
            }
        }
        return 1;
    }

    static int expand_palette(png *a, uint8_t *palette, int len, int pal_img_n)
    {
        VOGL_NOTE_UNUSED(len);
        uint32_t i, pixel_count = a->s.img_x * a->s.img_y;
        uint8_t *p, *temp_out, *orig = a->out;

        p = (uint8_t *)stb_malloc(pixel_count * pal_img_n);
        if (p == NULL)
            return e("outofmem", "Out of memory");

        // between here and stb_free(out) below, exitting would leak
        temp_out = p;

        if (pal_img_n == 3)
        {
            for (i = 0; i < pixel_count; ++i)
            {
                int n = orig[i] * 4;
                p[0] = palette[n];
                p[1] = palette[n + 1];
                p[2] = palette[n + 2];
                p += 3;
            }
        }
        else
        {
            for (i = 0; i < pixel_count; ++i)
            {
                int n = orig[i] * 4;
                p[0] = palette[n];
                p[1] = palette[n + 1];
                p[2] = palette[n + 2];
                p[3] = palette[n + 3];
                p += 4;
            }
        }
        stb_free(a->out);
        a->out = temp_out;
        return 1;
    }

    static int parse_png_file(png *z, int scan, int req_comp)
    {
        uint8_t palette[1024], pal_img_n = 0;
        uint8_t has_trans = 0, tc[3];
        uint32_t ioff = 0, idata_limit = 0, i, pal_len = 0;
        int first = 1, k, interlace = 0;
        stbi *s = &z->s;

        if (!check_png_header(s))
            return 0;

        if (scan == SCAN_type)
            return 1;

        for (;; first = 0)
        {
            chunk c = get_chunk_header(s);
            if (first && c.type != PNG_TYPE('I', 'H', 'D', 'R'))
                return e("first not IHDR", "Corrupt PNG");
            switch (c.type)
            {
                case PNG_TYPE('I', 'H', 'D', 'R')
                    :
                {
                    int depth, color, comp, filter;
                    if (!first)
                        return e("multiple IHDR", "Corrupt PNG");
                    if (c.length != 13)
                        return e("bad IHDR len", "Corrupt PNG");
                    s->img_x = get32(s);
                    if (s->img_x > (1 << 24))
                        return e("too large", "Very large image (corrupt?)");
                    s->img_y = get32(s);
                    if (s->img_y > (1 << 24))
                        return e("too large", "Very large image (corrupt?)");
                    depth = get8(s);
                    if (depth != 8)
                        return e("8bit only", "PNG not supported: 8-bit only");
                    color = get8(s);
                    if (color > 6)
                        return e("bad ctype", "Corrupt PNG");
                    if (color == 3)
                        pal_img_n = 3;
                    else if (color & 1)
                        return e("bad ctype", "Corrupt PNG");
                    comp = get8(s);
                    if (comp)
                        return e("bad comp method", "Corrupt PNG");
                    filter = get8(s);
                    if (filter)
                        return e("bad filter method", "Corrupt PNG");
                    interlace = get8(s);
                    if (interlace > 1)
                        return e("bad interlace method", "Corrupt PNG");
                    if (!s->img_x || !s->img_y)
                        return e("0-pixel image", "Corrupt PNG");
                    if (!pal_img_n)
                    {
                        s->img_n = (color & 2 ? 3 : 1) + (color & 4 ? 1 : 0);
                        if ((1 << 30) / s->img_x / s->img_n < s->img_y)
                            return e("too large", "Image too large to decode");
                        if (scan == SCAN_header)
                            return 1;
                    }
                    else
                    {
                        // if paletted, then pal_n is our final components, and
                        // img_n is # components to decompress/filter.
                        s->img_n = 1;
                        if ((1 << 30) / s->img_x / 4 < s->img_y)
                            return e("too large", "Corrupt PNG");
                        // if SCAN_header, have to scan to see if we have a tRNS
                    }
                    break;
                }

                case PNG_TYPE('P', 'L', 'T', 'E')
                    :
                {
                    if (c.length > 256 * 3)
                        return e("invalid PLTE", "Corrupt PNG");
                    pal_len = c.length / 3;
                    if (pal_len * 3 != c.length)
                        return e("invalid PLTE", "Corrupt PNG");
                    for (i = 0; i < pal_len; ++i)
                    {
                        palette[i * 4 + 0] = get8u(s);
                        palette[i * 4 + 1] = get8u(s);
                        palette[i * 4 + 2] = get8u(s);
                        palette[i * 4 + 3] = 255;
                    }
                    break;
                }

                case PNG_TYPE('t', 'R', 'N', 'S')
                    :
                {
                    if (z->idata)
                        return e("tRNS after IDAT", "Corrupt PNG");
                    if (pal_img_n)
                    {
                        if (scan == SCAN_header)
                        {
                            s->img_n = 4;
                            return 1;
                        }
                        if (pal_len == 0)
                            return e("tRNS before PLTE", "Corrupt PNG");
                        if (c.length > pal_len)
                            return e("bad tRNS len", "Corrupt PNG");
                        pal_img_n = 4;
                        for (i = 0; i < c.length; ++i)
                            palette[i * 4 + 3] = get8u(s);
                    }
                    else
                    {
                        if (!(s->img_n & 1))
                            return e("tRNS with alpha", "Corrupt PNG");
                        if (c.length != (uint32_t)s->img_n * 2)
                            return e("bad tRNS len", "Corrupt PNG");
                        has_trans = 1;
                        for (k = 0; k < s->img_n; ++k)
                            tc[k] = (uint8_t)get16(s); // non 8-bit images will be larger
                    }
                    break;
                }

                case PNG_TYPE('I', 'D', 'A', 'T')
                    :
                {
                    if (pal_img_n && !pal_len)
                        return e("no PLTE", "Corrupt PNG");
                    if (scan == SCAN_header)
                    {
                        s->img_n = pal_img_n;
                        return 1;
                    }
                    if (ioff + c.length > idata_limit)
                    {
                        uint8_t *p;
                        if (idata_limit == 0)
                            idata_limit = c.length > 4096 ? c.length : 4096;
                        while (ioff + c.length > idata_limit)
                            idata_limit *= 2;
                        p = (uint8_t *)stb_realloc(z->idata, idata_limit);
                        if (p == NULL)
                            return e("outofmem", "Out of memory");
                        z->idata = p;
                    }
#ifndef STBI_NO_STDIO
                    if (s->img_file)
                    {
                        if (fread(z->idata + ioff, 1, c.length, s->img_file) != c.length)
                            return e("outofdata", "Corrupt PNG");
                    }
                    else
#endif
                    {
                        memcpy(z->idata + ioff, s->img_buffer, c.length);
                        s->img_buffer += c.length;
                    }
                    ioff += c.length;
                    break;
                }

                case PNG_TYPE('I', 'E', 'N', 'D')
                    :
                {
                    uint32_t raw_len;
                    if (scan != SCAN_load)
                        return 1;
                    if (z->idata == NULL)
                        return e("no IDAT", "Corrupt PNG");
                    z->expanded = (uint8_t *)stbi_zlib_decode_malloc((char *)z->idata, ioff, (int *)&raw_len);
                    if (z->expanded == NULL)
                        return 0; // zlib should set error
                    stb_free(z->idata);
                    z->idata = NULL;
                    if ((req_comp == s->img_n + 1 && req_comp != 3 && !pal_img_n) || has_trans)
                        s->img_out_n = s->img_n + 1;
                    else
                        s->img_out_n = s->img_n;
                    if (!create_png_image(z, z->expanded, raw_len, s->img_out_n, interlace))
                        return 0;
                    if (has_trans)
                        if (!compute_transparency(z, tc, s->img_out_n))
                            return 0;
                    if (pal_img_n)
                    {
                        // pal_img_n == 3 or 4
                        s->img_n = pal_img_n; // record the actual colors we had
                        s->img_out_n = pal_img_n;
                        if (req_comp >= 3)
                            s->img_out_n = req_comp;
                        if (!expand_palette(z, palette, pal_len, s->img_out_n))
                            return 0;
                    }
                    stb_free(z->expanded);
                    z->expanded = NULL;
                    return 1;
                }

                default:
                    // if critical, fail
                    if ((c.type & (1 << 29)) == 0)
                    {
#ifndef STBI_NO_FAILURE_STRINGS
                        // not threadsafe
                        static char invalid_chunk[] = "XXXX chunk not known";
                        invalid_chunk[0] = (uint8_t)(c.type >> 24);
                        invalid_chunk[1] = (uint8_t)(c.type >> 16);
                        invalid_chunk[2] = (uint8_t)(c.type >> 8);
                        invalid_chunk[3] = (uint8_t)(c.type >> 0);
#endif
                        return e(invalid_chunk, "PNG not supported: unknown chunk type");
                    }
                    skip(s, c.length);
                    break;
            }
            // end of chunk, read and skip CRC
            get32(s);
        }
    }

    static unsigned char *do_png(png *p, int *x, int *y, int *n, int req_comp)
    {
        unsigned char *result = NULL;
        p->expanded = NULL;
        p->idata = NULL;
        p->out = NULL;
        if (req_comp < 0 || req_comp > 4)
            return epuc("bad req_comp", "Internal error");
        if (parse_png_file(p, SCAN_load, req_comp))
        {
            result = p->out;
            p->out = NULL;
            if (req_comp && req_comp != p->s.img_out_n)
            {
                result = convert_format(result, p->s.img_out_n, req_comp, p->s.img_x, p->s.img_y);
                p->s.img_out_n = req_comp;
                if (result == NULL)
                    return result;
            }
            *x = p->s.img_x;
            *y = p->s.img_y;
            if (n)
                *n = p->s.img_n;
        }
        stb_free(p->out);
        p->out = NULL;
        stb_free(p->expanded);
        p->expanded = NULL;
        stb_free(p->idata);
        p->idata = NULL;

        return result;
    }

#ifndef STBI_NO_STDIO
    unsigned char *stbi_png_load_from_file(FILE *f, int *x, int *y, int *comp, int req_comp)
    {
        png p;
        start_file(&p.s, f);
        return do_png(&p, x, y, comp, req_comp);
    }

    unsigned char *stbi_png_load(char const *filename, int *x, int *y, int *comp, int req_comp)
    {
        unsigned char *data;
        FILE *f = fopen(filename, "rb");
        if (!f)
            return NULL;
        data = stbi_png_load_from_file(f, x, y, comp, req_comp);
        fclose(f);
        return data;
    }
#endif

    unsigned char *stbi_png_load_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp)
    {
        png p;
        start_mem(&p.s, buffer, len);
        return do_png(&p, x, y, comp, req_comp);
    }

#ifndef STBI_NO_STDIO
    int stbi_png_test_file(FILE *f)
    {
        png p;
        int n, r;
        n = (int)ftell(f);
        start_file(&p.s, f);
        r = parse_png_file(&p, SCAN_type, STBI_default);
        fseek(f, n, SEEK_SET);
        return r;
    }
#endif

    int stbi_png_test_memory(stbi_uc const *buffer, int len)
    {
        png p;
        start_mem(&p.s, buffer, len);
        return parse_png_file(&p, SCAN_type, STBI_default);
    }

// TODO: load header from png
#ifndef STBI_NO_STDIO
    int stbi_png_info(char const *filename, int *x, int *y, int *comp)
    {
        png p;
        FILE *f = fopen(filename, "rb");
        if (!f)
            return 0;
        start_file(&p.s, f);
        if (parse_png_file(&p, SCAN_header, 0))
        {
            if (x)
                *x = p.s.img_x;
            if (y)
                *y = p.s.img_y;
            if (comp)
                *comp = p.s.img_n;
            fclose(f);
            return 1;
        }
        fclose(f);
        return 0;
    }

    extern int stbi_png_info_from_file(FILE *f, int *x, int *y, int *comp);
#endif
    extern int stbi_png_info_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp);

    // Microsoft/Windows BMP image

    static int bmp_test(stbi *s)
    {
        int sz;
        if (get8(s) != 'B')
            return 0;
        if (get8(s) != 'M')
            return 0;
        get32le(s); // discard filesize
        get16le(s); // discard reserved
        get16le(s); // discard reserved
        get32le(s); // discard data offset
        sz = get32le(s);
        if (sz == 12 || sz == 40 || sz == 56 || sz == 108)
            return 1;
        return 0;
    }

#ifndef STBI_NO_STDIO
    int stbi_bmp_test_file(FILE *f)
    {
        stbi s;
        int r, n = (int)ftell(f);
        start_file(&s, f);
        r = bmp_test(&s);
        fseek(f, n, SEEK_SET);
        return r;
    }
#endif

    int stbi_bmp_test_memory(stbi_uc const *buffer, int len)
    {
        stbi s;
        start_mem(&s, buffer, len);
        return bmp_test(&s);
    }

    // returns 0..31 for the highest set bit
    static int high_bit(unsigned int z)
    {
        int n = 0;
        if (z == 0)
            return -1;
        if (z >= 0x10000)
            n += 16, z >>= 16;
        if (z >= 0x00100)
            n += 8, z >>= 8;
        if (z >= 0x00010)
            n += 4, z >>= 4;
        if (z >= 0x00004)
            n += 2, z >>= 2;
        if (z >= 0x00002)
            n += 1, z >>= 1;
        return n;
    }

    static int bitcount(unsigned int a)
    {
        a = (a & 0x55555555) + ((a >> 1) & 0x55555555); // max 2
        a = (a & 0x33333333) + ((a >> 2) & 0x33333333); // max 4
        a = (a + (a >> 4)) & 0x0f0f0f0f;                // max 8 per 4, now 8 bits
        a = (a + (a >> 8));                             // max 16 per 8 bits
        a = (a + (a >> 16));                            // max 32 per 8 bits
        return a & 0xff;
    }

    static int shiftsigned(int v, int shift, int bits)
    {
        int result;
        int z = 0;

        if (shift < 0)
            v <<= -shift;
        else
            v >>= shift;
        result = v;

        z = bits;
        while (z < 8)
        {
            result += v >> z;
            z += bits;
        }
        return result;
    }

    static stbi_uc *bmp_load(stbi *s, int *x, int *y, int *comp, int req_comp)
    {
        uint8_t *out;
        unsigned int mr = 0, mg = 0, mb = 0, ma = 0, fake_a = 0;
        (void)fake_a;
        stbi_uc pal[256][4];
        int psize = 0, i, j, compress = 0, width;
        int bpp, flip_vertically, pad, target, offset, hsz;
        if (get8(s) != 'B' || get8(s) != 'M')
            return epuc("not BMP", "Corrupt BMP");
        get32le(s); // discard filesize
        get16le(s); // discard reserved
        get16le(s); // discard reserved
        offset = get32le(s);
        hsz = get32le(s);
        if (hsz != 12 && hsz != 40 && hsz != 56 && hsz != 108)
            return epuc("unknown BMP", "BMP type not supported: unknown");
        failure_reason = "bad BMP";
        if (hsz == 12)
        {
            s->img_x = get16le(s);
            s->img_y = get16le(s);
        }
        else
        {
            s->img_x = get32le(s);
            s->img_y = get32le(s);
        }
        if (get16le(s) != 1)
            return 0;
        bpp = get16le(s);
        if (bpp == 1)
            return epuc("monochrome", "BMP type not supported: 1-bit");
        flip_vertically = ((int)s->img_y) > 0;
        s->img_y = abs((int)s->img_y);
        if (hsz == 12)
        {
            if (bpp < 24)
                psize = (offset - 14 - 24) / 3;
        }
        else
        {
            compress = get32le(s);
            if (compress == 1 || compress == 2)
                return epuc("BMP RLE", "BMP type not supported: RLE");
            get32le(s); // discard sizeof
            get32le(s); // discard hres
            get32le(s); // discard vres
            get32le(s); // discard colorsused
            get32le(s); // discard max important
            if (hsz == 40 || hsz == 56)
            {
                if (hsz == 56)
                {
                    get32le(s);
                    get32le(s);
                    get32le(s);
                    get32le(s);
                }
                if (bpp == 16 || bpp == 32)
                {
                    mr = mg = mb = 0;
                    if (compress == 0)
                    {
                        if (bpp == 32)
                        {
                            mr = 0xff << 16;
                            mg = 0xff << 8;
                            mb = 0xff << 0;
                            ma = (unsigned int)0xff << 24;
                            fake_a = 1; // @TODO: check for cases like alpha value is all 0 and switch it to 255
                        }
                        else
                        {
                            mr = 31 << 10;
                            mg = 31 << 5;
                            mb = 31 << 0;
                        }
                    }
                    else if (compress == 3)
                    {
                        mr = get32le(s);
                        mg = get32le(s);
                        mb = get32le(s);
                        // not documented, but generated by photoshop and handled by mspaint
                        if (mr == mg && mg == mb)
                        {
                            // ?!?!?
                            return NULL;
                        }
                    }
                    else
                        return NULL;
                }
            }
            else
            {
                assert(hsz == 108);
                mr = get32le(s);
                mg = get32le(s);
                mb = get32le(s);
                ma = get32le(s);
                get32le(s); // discard color space
                for (i = 0; i < 12; ++i)
                    get32le(s); // discard color space parameters
            }
            if (bpp < 16)
                psize = (offset - 14 - hsz) >> 2;
        }
        s->img_n = ma ? 4 : 3;
        if (req_comp && req_comp >= 3) // we can directly decode 3 or 4
            target = req_comp;
        else
            target = s->img_n; // if they want monochrome, we'll post-convert
        out = (stbi_uc *)stb_malloc(target * s->img_x * s->img_y);
        if (!out)
            return epuc("outofmem", "Out of memory");
        if (bpp < 16)
        {
            int z = 0;
            if (psize == 0 || psize > 256)
            {
                stb_free(out);
                return epuc("invalid", "Corrupt BMP");
            }
            for (i = 0; i < psize; ++i)
            {
                pal[i][2] = get8(s);
                pal[i][1] = get8(s);
                pal[i][0] = get8(s);
                if (hsz != 12)
                    get8(s);
                pal[i][3] = 255;
            }
            skip(s, offset - 14 - hsz - psize * (hsz == 12 ? 3 : 4));
            if (bpp == 4)
                width = (s->img_x + 1) >> 1;
            else if (bpp == 8)
                width = s->img_x;
            else
            {
                stb_free(out);
                return epuc("bad bpp", "Corrupt BMP");
            }
            pad = (-width) & 3;
            for (j = 0; j < (int)s->img_y; ++j)
            {
                for (i = 0; i < (int)s->img_x; i += 2)
                {
                    int v = get8(s), v2 = 0;
                    if (bpp == 4)
                    {
                        v2 = v & 15;
                        v >>= 4;
                    }
                    out[z++] = pal[v][0];
                    out[z++] = pal[v][1];
                    out[z++] = pal[v][2];
                    if (target == 4)
                        out[z++] = 255;
                    if (i + 1 == (int)s->img_x)
                        break;
                    v = (bpp == 8) ? get8(s) : v2;
                    out[z++] = pal[v][0];
                    out[z++] = pal[v][1];
                    out[z++] = pal[v][2];
                    if (target == 4)
                        out[z++] = 255;
                }
                skip(s, pad);
            }
        }
        else
        {
            int rshift = 0, gshift = 0, bshift = 0, ashift = 0, rcount = 0, gcount = 0, bcount = 0, acount = 0;
            int z = 0;
            int easy = 0;
            skip(s, offset - 14 - hsz);
            if (bpp == 24)
                width = 3 * s->img_x;
            else if (bpp == 16)
                width = 2 * s->img_x;
            else /* bpp = 32 and pad = 0 */
                width = 0;
            pad = (-width) & 3;
            if (bpp == 24)
            {
                easy = 1;
            }
            else if (bpp == 32)
            {
                if (mb == 0xff && mg == 0xff00 && mr == 0xff000000 && ma == 0xff000000)
                    easy = 2;
            }
            if (!easy)
            {
                if (!mr || !mg || !mb)
                    return epuc("bad masks", "Corrupt BMP");
                // right shift amt to put high bit in position #7
                rshift = high_bit(mr) - 7;
                rcount = bitcount(mr);
                gshift = high_bit(mg) - 7;
                gcount = bitcount(mr);
                bshift = high_bit(mb) - 7;
                bcount = bitcount(mr);
                ashift = high_bit(ma) - 7;
                acount = bitcount(mr);
            }
            for (j = 0; j < (int)s->img_y; ++j)
            {
                if (easy)
                {
                    for (i = 0; i < (int)s->img_x; ++i)
                    {
                        int a;
                        out[z + 2] = get8(s);
                        out[z + 1] = get8(s);
                        out[z + 0] = get8(s);
                        z += 3;
                        a = (easy == 2 ? get8(s) : 255);
                        if (target == 4)
                            out[z++] = a;
                    }
                }
                else
                {
                    for (i = 0; i < (int)s->img_x; ++i)
                    {
                        uint32_t v = (bpp == 16 ? get16le(s) : get32le(s));
                        int a;
                        out[z++] = shiftsigned(v & mr, rshift, rcount);
                        out[z++] = shiftsigned(v & mg, gshift, gcount);
                        out[z++] = shiftsigned(v & mb, bshift, bcount);
                        a = (ma ? shiftsigned(v & ma, ashift, acount) : 255);
                        if (target == 4)
                            out[z++] = a;
                    }
                }
                skip(s, pad);
            }
        }
        if (flip_vertically)
        {
            stbi_uc t;
            for (j = 0; j<(int)s->img_y>> 1; ++j)
            {
                stbi_uc *p1 = out + j * s->img_x * target;
                stbi_uc *p2 = out + (s->img_y - 1 - j) * s->img_x * target;
                for (i = 0; i < (int)s->img_x * target; ++i)
                {
                    t = p1[i], p1[i] = p2[i], p2[i] = t;
                }
            }
        }

        if (req_comp && req_comp != target)
        {
            out = convert_format(out, target, req_comp, s->img_x, s->img_y);
            if (out == NULL)
                return out; // convert_format frees input on failure
        }

        *x = s->img_x;
        *y = s->img_y;
        if (comp)
            *comp = target;
        return out;
    }

#ifndef STBI_NO_STDIO
    stbi_uc *stbi_bmp_load(char const *filename, int *x, int *y, int *comp, int req_comp)
    {
        stbi_uc *data;
        FILE *f = fopen(filename, "rb");
        if (!f)
            return NULL;
        data = stbi_bmp_load_from_file(f, x, y, comp, req_comp);
        fclose(f);
        return data;
    }

    stbi_uc *stbi_bmp_load_from_file(FILE *f, int *x, int *y, int *comp, int req_comp)
    {
        stbi s;
        start_file(&s, f);
        return bmp_load(&s, x, y, comp, req_comp);
    }
#endif

    stbi_uc *stbi_bmp_load_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp)
    {
        stbi s;
        start_mem(&s, buffer, len);
        return bmp_load(&s, x, y, comp, req_comp);
    }

    // Targa Truevision - TGA
    // by Jonathan Dummer

    static int tga_test(stbi *s)
    {
        int sz;
        get8u(s);      //	discard Offset
        sz = get8u(s); //	color type
        if (sz > 1)
            return 0;  //	only RGB or indexed allowed
        sz = get8u(s); //	image type
        if ((sz != 1) && (sz != 2) && (sz != 3) && (sz != 9) && (sz != 10) && (sz != 11))
            return 0; //	only RGB or grey allowed, +/- RLE
        get16(s);     //	discard palette start
        get16(s);     //	discard palette length
        get8(s);      //	discard bits per palette color entry
        get16(s);     //	discard x origin
        get16(s);     //	discard y origin
        if (get16(s) < 1)
            return 0; //	test width
        if (get16(s) < 1)
            return 0; //	test height
        sz = get8(s); //	bits per pixel
        if ((sz != 8) && (sz != 16) && (sz != 24) && (sz != 32))
            return 0; //	only RGB or RGBA or grey allowed
        return 1;     //	seems to have passed everything
    }

#ifndef STBI_NO_STDIO
    int stbi_tga_test_file(FILE *f)
    {
        stbi s;
        int r, n = (int)ftell(f);
        start_file(&s, f);
        r = tga_test(&s);
        fseek(f, n, SEEK_SET);
        return r;
    }
#endif

    int stbi_tga_test_memory(stbi_uc const *buffer, int len)
    {
        stbi s;
        start_mem(&s, buffer, len);
        return tga_test(&s);
    }

    static stbi_uc *tga_load(stbi *s, int *x, int *y, int *comp, int req_comp)
    {
        //	read in the TGA header stuff
        int tga_offset = get8u(s);
        int tga_indexed = get8u(s);
        int tga_image_type = get8u(s);
        int tga_is_RLE = 0;
        int tga_palette_start = get16le(s);
        int tga_palette_len = get16le(s);
        int tga_palette_bits = get8u(s);
        int tga_x_origin = get16le(s);
        int tga_y_origin = get16le(s);
        int tga_width = get16le(s);
        int tga_height = get16le(s);
        int tga_bits_per_pixel = get8u(s);
        int tga_inverted = get8u(s);
        //	image data
        unsigned char *tga_data;
        unsigned char *tga_palette = NULL;
        int i, j;
        unsigned char raw_data[4];
        unsigned char trans_data[4] = { 0, 0, 0, 0 };
        int RLE_count = 0;
        int RLE_repeating = 0;
        int read_next_pixel = 1;
        //	do a tiny bit of precessing
        if (tga_image_type >= 8)
        {
            tga_image_type -= 8;
            tga_is_RLE = 1;
        }
        /* int tga_alpha_bits = tga_inverted & 15; */
        tga_inverted = 1 - ((tga_inverted >> 5) & 1);

        //	error check
        if ( //(tga_indexed) ||
                (tga_width < 1) || (tga_height < 1) ||
                (tga_image_type < 1) || (tga_image_type > 3) ||
                ((tga_bits_per_pixel != 8) && (tga_bits_per_pixel != 16) &&
                 (tga_bits_per_pixel != 24) && (tga_bits_per_pixel != 32)))
        {
            return NULL;
        }

        //	If I'm paletted, then I'll use the number of bits from the palette
        if (tga_indexed)
        {
            tga_bits_per_pixel = tga_palette_bits;
        }

        //	tga info
        *x = tga_width;
        *y = tga_height;
        if ((req_comp < 1) || (req_comp > 4))
        {
            //	just use whatever the file was
            req_comp = tga_bits_per_pixel / 8;
            *comp = req_comp;
        }
        else
        {
            //	force a new number of components
            *comp = tga_bits_per_pixel / 8;
        }
        tga_data = (unsigned char *)stb_malloc(tga_width * tga_height * req_comp);

        //	skip to the data's starting position (offset usually = 0)
        skip(s, tga_offset);
        //	do I need to load a palette?
        if (tga_indexed)
        {
            //	any data to skip? (offset usually = 0)
            skip(s, tga_palette_start);
            //	load the palette
            tga_palette = (unsigned char *)stb_malloc(tga_palette_len * tga_palette_bits / 8);
            getn(s, tga_palette, tga_palette_len * tga_palette_bits / 8);
        }
        //	load the data
        for (i = 0; i < tga_width * tga_height; ++i)
        {
            //	if I'm in RLE mode, do I need to get a RLE chunk?
            if (tga_is_RLE)
            {
                if (RLE_count == 0)
                {
                    //	yep, get the next byte as a RLE command
                    int RLE_cmd = get8u(s);
                    RLE_count = 1 + (RLE_cmd & 127);
                    RLE_repeating = RLE_cmd >> 7;
                    read_next_pixel = 1;
                }
                else if (!RLE_repeating)
                {
                    read_next_pixel = 1;
                }
            }
            else
            {
                read_next_pixel = 1;
            }
            //	OK, if I need to read a pixel, do it now
            if (read_next_pixel)
            {
                //	load however much data we did have
                if (tga_indexed)
                {
                    //	read in 1 byte, then perform the lookup
                    int pal_idx = get8u(s);
                    if (pal_idx >= tga_palette_len)
                    {
                        //	invalid index
                        pal_idx = 0;
                    }
                    pal_idx *= tga_bits_per_pixel / 8;
                    for (j = 0; j * 8 < tga_bits_per_pixel; ++j)
                    {
                        raw_data[j] = tga_palette[pal_idx + j];
                    }
                }
                else
                {
                    //	read in the data raw
                    for (j = 0; j * 8 < tga_bits_per_pixel; ++j)
                    {
                        raw_data[j] = get8u(s);
                    }
                }
                //	convert raw to the intermediate format
                switch (tga_bits_per_pixel)
                {
                    case 8:
                        //	Luminous => RGBA
                        trans_data[0] = raw_data[0];
                        trans_data[1] = raw_data[0];
                        trans_data[2] = raw_data[0];
                        trans_data[3] = 255;
                        break;
                    case 16:
                        //	Luminous,Alpha => RGBA
                        trans_data[0] = raw_data[0];
                        trans_data[1] = raw_data[0];
                        trans_data[2] = raw_data[0];
                        trans_data[3] = raw_data[1];
                        break;
                    case 24:
                        //	BGR => RGBA
                        trans_data[0] = raw_data[2];
                        trans_data[1] = raw_data[1];
                        trans_data[2] = raw_data[0];
                        trans_data[3] = 255;
                        break;
                    case 32:
                        //	BGRA => RGBA
                        trans_data[0] = raw_data[2];
                        trans_data[1] = raw_data[1];
                        trans_data[2] = raw_data[0];
                        trans_data[3] = raw_data[3];
                        break;
                }
                //	clear the reading flag for the next pixel
                read_next_pixel = 0;
            } // end of reading a pixel
            //	convert to final format
            switch (req_comp)
            {
                case 1:
                    //	RGBA => Luminance
                    tga_data[i * req_comp + 0] = compute_y(trans_data[0], trans_data[1], trans_data[2]);
                    break;
                case 2:
                    //	RGBA => Luminance,Alpha
                    tga_data[i * req_comp + 0] = compute_y(trans_data[0], trans_data[1], trans_data[2]);
                    tga_data[i * req_comp + 1] = trans_data[3];
                    break;
                case 3:
                    //	RGBA => RGB
                    tga_data[i * req_comp + 0] = trans_data[0];
                    tga_data[i * req_comp + 1] = trans_data[1];
                    tga_data[i * req_comp + 2] = trans_data[2];
                    break;
                case 4:
                    //	RGBA => RGBA
                    tga_data[i * req_comp + 0] = trans_data[0];
                    tga_data[i * req_comp + 1] = trans_data[1];
                    tga_data[i * req_comp + 2] = trans_data[2];
                    tga_data[i * req_comp + 3] = trans_data[3];
                    break;
            }
            //	in case we're in RLE mode, keep counting down
            --RLE_count;
        }
        //	do I need to invert the image?
        if (tga_inverted)
        {
            for (j = 0; j * 2 < tga_height; ++j)
            {
                int index1 = j * tga_width * req_comp;
                int index2 = (tga_height - 1 - j) * tga_width * req_comp;
                for (i = tga_width * req_comp; i > 0; --i)
                {
                    unsigned char temp = tga_data[index1];
                    tga_data[index1] = tga_data[index2];
                    tga_data[index2] = temp;
                    ++index1;
                    ++index2;
                }
            }
        }
        //	clear my palette, if I had one
        if (tga_palette != NULL)
        {
            stb_free(tga_palette);
        }
        //	the things I do to get rid of an error message, and yet keep
        //	Microsoft's C compilers happy... [8^(
        tga_palette_start = tga_palette_len = tga_palette_bits =
            tga_x_origin = tga_y_origin = 0;
        //	OK, done
        return tga_data;
    }

#ifndef STBI_NO_STDIO
    stbi_uc *stbi_tga_load(char const *filename, int *x, int *y, int *comp, int req_comp)
    {
        stbi_uc *data;
        FILE *f = fopen(filename, "rb");
        if (!f)
            return NULL;
        data = stbi_tga_load_from_file(f, x, y, comp, req_comp);
        fclose(f);
        return data;
    }

    stbi_uc *stbi_tga_load_from_file(FILE *f, int *x, int *y, int *comp, int req_comp)
    {
        stbi s;
        start_file(&s, f);
        return tga_load(&s, x, y, comp, req_comp);
    }
#endif

    stbi_uc *stbi_tga_load_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp)
    {
        stbi s;
        start_mem(&s, buffer, len);
        return tga_load(&s, x, y, comp, req_comp);
    }

    // *************************************************************************************************
    // Photoshop PSD loader -- PD by Thatcher Ulrich, integration by Nicholas Schulz, tweaked by STB

    static int psd_test(stbi *s)
    {
        if (get32(s) != 0x38425053)
            return 0; // "8BPS"
        else
            return 1;
    }

#ifndef STBI_NO_STDIO
    int stbi_psd_test_file(FILE *f)
    {
        stbi s;
        int r, n = (int)ftell(f);
        memset(&s, 0, sizeof(s));
        start_file(&s, f);
        r = psd_test(&s);
        fseek(f, n, SEEK_SET);
        return r;
    }
#endif

    int stbi_psd_test_memory(stbi_uc const *buffer, int len)
    {
        stbi s;
        start_mem(&s, buffer, len);
        return psd_test(&s);
    }

    static stbi_uc *psd_load(stbi *s, int *x, int *y, int *comp, int req_comp)
    {
        int pixelCount;
        int channelCount, compression;
        int channel, i, count, len;
        int w, h;
        uint8_t *out;

        // Check identifier
        if (get32(s) != 0x38425053) // "8BPS"
            return epuc("not PSD", "Corrupt PSD image");

        // Check file type version.
        if (get16(s) != 1)
            return epuc("wrong version", "Unsupported version of PSD image");

        // Skip 6 reserved bytes.
        skip(s, 6);

        // Read the number of channels (R, G, B, A, etc).
        channelCount = get16(s);
        if (channelCount < 0 || channelCount > 16)
            return epuc("wrong channel count", "Unsupported number of channels in PSD image");

        // Read the rows and columns of the image.
        h = get32(s);
        w = get32(s);

        // Make sure the depth is 8 bits.
        if (get16(s) != 8)
            return epuc("unsupported bit depth", "PSD bit depth is not 8 bit");

        // Make sure the color mode is RGB.
        // Valid options are:
        //   0: Bitmap
        //   1: Grayscale
        //   2: Indexed color
        //   3: RGB color
        //   4: CMYK color
        //   7: Multichannel
        //   8: Duotone
        //   9: Lab color
        if (get16(s) != 3)
            return epuc("wrong color format", "PSD is not in RGB color format");

        // Skip the Mode Data.  (It's the palette for indexed color; other info for other modes.)
        skip(s, get32(s));

        // Skip the image resources.  (resolution, pen tool paths, etc)
        skip(s, get32(s));

        // Skip the reserved data.
        skip(s, get32(s));

        // Find out if the data is compressed.
        // Known values:
        //   0: no compression
        //   1: RLE compressed
        compression = get16(s);
        if (compression > 1)
            return epuc("bad compression", "PSD has an unknown compression format");

        // Create the destination image.
        out = (stbi_uc *)stb_malloc(4 * w * h);
        if (!out)
            return epuc("outofmem", "Out of memory");
        pixelCount = w * h;

        // Initialize the data to zero.
        //memset( out, 0, pixelCount * 4 );

        // Finally, the image data.
        if (compression)
        {
            // RLE as used by .PSD and .TIFF
            // Loop until you get the number of unpacked bytes you are expecting:
            //     Read the next source byte into n.
            //     If n is between 0 and 127 inclusive, copy the next n+1 bytes literally.
            //     Else if n is between -127 and -1 inclusive, copy the next byte -n+1 times.
            //     Else if n is 128, noop.
            // Endloop

            // The RLE-compressed data is preceeded by a 2-byte data count for each row in the data,
            // which we're going to just skip.
            skip(s, h * channelCount * 2);

            // Read the RLE data by channel.
            for (channel = 0; channel < 4; channel++)
            {
                uint8_t *p;

                p = out + channel;
                if (channel >= channelCount)
                {
                    // Fill this channel with default data.
                    for (i = 0; i < pixelCount; i++)
                        *p = (channel == 3 ? 255 : 0), p += 4;
                }
                else
                {
                    // Read the RLE data.
                    count = 0;
                    while (count < pixelCount)
                    {
                        len = get8(s);
                        if (len == 128)
                        {
                            // No-op.
                        }
                        else if (len < 128)
                        {
                            // Copy next len+1 bytes literally.
                            len++;
                            count += len;
                            while (len)
                            {
                                *p = get8(s);
                                p += 4;
                                len--;
                            }
                        }
                        else if (len > 128)
                        {
                            uint32_t val;
                            // Next -len+1 bytes in the dest are replicated from next source byte.
                            // (Interpret len as a negative 8-bit int.)
                            len ^= 0x0FF;
                            len += 2;
                            val = get8(s);
                            count += len;
                            while (len)
                            {
                                *p = val;
                                p += 4;
                                len--;
                            }
                        }
                    }
                }
            }
        }
        else
        {
            // We're at the raw image data.  It's each channel in order (Red, Green, Blue, Alpha, ...)
            // where each channel consists of an 8-bit value for each pixel in the image.

            // Read the data by channel.
            for (channel = 0; channel < 4; channel++)
            {
                uint8_t *p;

                p = out + channel;
                if (channel > channelCount)
                {
                    // Fill this channel with default data.
                    for (i = 0; i < pixelCount; i++)
                        *p = channel == 3 ? 255 : 0, p += 4;
                }
                else
                {
                    // Read the data.
                    count = 0;
                    for (i = 0; i < pixelCount; i++)
                        *p = get8(s), p += 4;
                }
            }
        }

        if (req_comp && req_comp != 4)
        {
            out = convert_format(out, 4, req_comp, w, h);
            if (out == NULL)
                return out; // convert_format frees input on failure
        }

        if (comp)
            *comp = channelCount;
        *y = h;
        *x = w;

        return out;
    }

#ifndef STBI_NO_STDIO
    stbi_uc *stbi_psd_load(char const *filename, int *x, int *y, int *comp, int req_comp)
    {
        stbi_uc *data;
        FILE *f = fopen(filename, "rb");
        if (!f)
            return NULL;
        data = stbi_psd_load_from_file(f, x, y, comp, req_comp);
        fclose(f);
        return data;
    }

    stbi_uc *stbi_psd_load_from_file(FILE *f, int *x, int *y, int *comp, int req_comp)
    {
        stbi s;
        start_file(&s, f);
        return psd_load(&s, x, y, comp, req_comp);
    }
#endif

    stbi_uc *stbi_psd_load_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp)
    {
        stbi s;
        start_mem(&s, buffer, len);
        return psd_load(&s, x, y, comp, req_comp);
    }

// *************************************************************************************************
// Radiance RGBE HDR loader
// originally by Nicolas Schulz
#ifndef STBI_NO_HDR
    static int hdr_test(stbi *s)
    {
        const char *signature = "#?RADIANCE\n";
        int i;
        for (i = 0; signature[i]; ++i)
            if (get8(s) != signature[i])
                return 0;
        return 1;
    }

    int stbi_hdr_test_memory(stbi_uc const *buffer, int len)
    {
        stbi s;
        start_mem(&s, buffer, len);
        return hdr_test(&s);
    }

#ifndef STBI_NO_STDIO
    int stbi_hdr_test_file(FILE *f)
    {
        stbi s;
        int r, n = (int)ftell(f);
        memset(&s, 0, sizeof(s));
        start_file(&s, f);
        r = hdr_test(&s);
        fseek(f, n, SEEK_SET);
        return r;
    }
#endif

#define HDR_BUFLEN 1024
    static char *hdr_gettoken(stbi *z, char *buffer)
    {
        int len = 0;
        //char *s = buffer;
        char c = '\0';

        c = get8(z);

        while (!at_eof(z) && c != '\n')
        {
            buffer[len++] = c;
            if (len == HDR_BUFLEN - 1)
            {
                // flush to end of line
                while (!at_eof(z) && get8(z) != '\n')
                    ;
                break;
            }
            c = get8(z);
        }

        buffer[len] = 0;
        return buffer;
    }

    static void hdr_convert(float *output, stbi_uc *input, int req_comp)
    {
        if (input[3] != 0)
        {
            float f1;
            // Exponent
            f1 = (float)ldexp(1.0f, input[3] - (int)(128 + 8));
            if (req_comp <= 2)
                output[0] = (input[0] + input[1] + input[2]) * f1 / 3;
            else
            {
                output[0] = input[0] * f1;
                output[1] = input[1] * f1;
                output[2] = input[2] * f1;
            }
            if (req_comp == 2)
                output[1] = 1;
            if (req_comp == 4)
                output[3] = 1;
        }
        else
        {
            switch (req_comp)
            {
                case 4:
                    output[3] = 1; /* fallthrough */
                case 3:
                    output[0] = output[1] = output[2] = 0;
                    break;
                case 2:
                    output[1] = 1; /* fallthrough */
                case 1:
                    output[0] = 0;
                    break;
            }
        }
    }

    static float *hdr_load(stbi *s, int *x, int *y, int *comp, int req_comp)
    {
        char buffer[HDR_BUFLEN];
        char *token;
        int valid = 0;
        int width, height;
        stbi_uc *scanline;
        float *hdr_data;
        int len;
        unsigned char count, value;
        int i, j, k, c1, c2, z;

        // Check identifier
        if (strcmp(hdr_gettoken(s, buffer), "#?RADIANCE") != 0)
            return epf("not HDR", "Corrupt HDR image");

        // Parse header
        while (1)
        {
            token = hdr_gettoken(s, buffer);
            if (token[0] == 0)
                break;
            if (strcmp(token, "FORMAT=32-bit_rle_rgbe") == 0)
                valid = 1;
        }

        if (!valid)
            return epf("unsupported format", "Unsupported HDR format");

        // Parse width and height
        // can't use sscanf() if we're not using stdio!
        token = hdr_gettoken(s, buffer);
        if (strncmp(token, "-Y ", 3))
            return epf("unsupported data layout", "Unsupported HDR format");
        token += 3;
        height = (int)strtol(token, &token, 10);
        while (*token == ' ')
            ++token;
        if (strncmp(token, "+X ", 3))
            return epf("unsupported data layout", "Unsupported HDR format");
        token += 3;
        width = (int)strtol(token, NULL, 10);

        *x = width;
        *y = height;

        *comp = 3;
        if (req_comp == 0)
            req_comp = 3;

        // Read data
        hdr_data = (float *)stb_malloc(height * width * req_comp * sizeof(float));

        // Load image data
        // image data is stored as some number of sca
        if (width < 8 || width >= 32768)
        {
            // Read flat data
            for (j = 0; j < height; ++j)
            {
                for (i = 0; i < width; ++i)
                {
                    stbi_uc rgbe[4];
                main_decode_loop:
                    getn(s, rgbe, 4);
                    hdr_convert(hdr_data + j * width * req_comp + i * req_comp, rgbe, req_comp);
                }
            }
        }
        else
        {
            // Read RLE-encoded data
            scanline = NULL;

            for (j = 0; j < height; ++j)
            {
                c1 = get8(s);
                c2 = get8(s);
                len = get8(s);
                if (c1 != 2 || c2 != 2 || (len & 0x80))
                {
                    // not run-length encoded, so we have to actually use THIS data as a decoded
                    // pixel (note this can't be a valid pixel--one of RGB must be >= 128)
                    stbi_uc rgbe[4] = {(stbi_uc)c1, (stbi_uc)c2, (stbi_uc)len, (stbi_uc)get8(s) };
                    hdr_convert(hdr_data, rgbe, req_comp);
                    i = 1;
                    j = 0;
                    stb_free(scanline);
                    goto main_decode_loop; // yes, this is fucking insane; blame the fucking insane format
                }
                len <<= 8;
                len |= get8(s);
                if (len != width)
                {
                    stb_free(hdr_data);
                    stb_free(scanline);
                    return epf("invalid decoded scanline length", "corrupt HDR");
                }
                if (scanline == NULL)
                    scanline = (stbi_uc *)stb_malloc(width * 4);

                for (k = 0; k < 4; ++k)
                {
                    i = 0;
                    while (i < width)
                    {
                        count = get8(s);
                        if (count > 128)
                        {
                            // Run
                            value = get8(s);
                            count -= 128;
                            for (z = 0; z < count; ++z)
                                scanline[i++ * 4 + k] = value;
                        }
                        else
                        {
                            // Dump
                            for (z = 0; z < count; ++z)
                                scanline[i++ * 4 + k] = get8(s);
                        }
                    }
                }
                for (i = 0; i < width; ++i)
                    hdr_convert(hdr_data + (j * width + i) * req_comp, scanline + i * 4, req_comp);
            }
            stb_free(scanline);
        }

        return hdr_data;
    }

#ifndef STBI_NO_STDIO
    float *stbi_hdr_load_from_file(FILE *f, int *x, int *y, int *comp, int req_comp)
    {
        stbi s;
        start_file(&s, f);
        return hdr_load(&s, x, y, comp, req_comp);
    }
#endif

    float *stbi_hdr_load_from_memory(stbi_uc const *buffer, int len, int *x, int *y, int *comp, int req_comp)
    {
        stbi s;
        start_mem(&s, buffer, len);
        return hdr_load(&s, x, y, comp, req_comp);
    }

#endif // STBI_NO_HDR

/////////////////////// write image ///////////////////////

#ifndef STBI_NO_WRITE

    static void write8(FILE *f, int x)
    {
        uint8_t z = (uint8_t)x;
        fwrite(&z, 1, 1, f);
    }

    static void writefv(FILE *f, char *fmt, va_list v)
    {
        while (*fmt)
        {
            switch (*fmt++)
            {
                case ' ':
                    break;
                case '1':
                {
                    uint8_t x = va_arg(v, int);
                    write8(f, x);
                    break;
                }
                case '2':
                {
                    int16_t x = va_arg(v, int);
                    write8(f, x);
                    write8(f, x >> 8);
                    break;
                }
                case '4':
                {
                    int32_t x = va_arg(v, int);
                    write8(f, x);
                    write8(f, x >> 8);
                    write8(f, x >> 16);
                    write8(f, x >> 24);
                    break;
                }
                default:
                    assert(0);
                    va_end(v);
                    return;
            }
        }
    }

    static void writef(FILE *f, char *fmt, ...)
    {
        va_list v;
        va_start(v, fmt);
        writefv(f, fmt, v);
        va_end(v);
    }

    static void write_pixels(FILE *f, int rgb_dir, int vdir, int x, int y, int comp, const void *data, int write_alpha, int scanline_pad)
    {
        uint8_t bg[3] = { 255, 0, 255 }, px[3];
        uint32_t zero = 0;
        int i, j, k, j_end;

        if (vdir < 0)
            j_end = -1, j = y - 1;
        else
            j_end = y, j = 0;

        for (; j != j_end; j += vdir)
        {
            for (i = 0; i < x; ++i)
            {
                uint8_t *d = (uint8_t *)data + (j * x + i) * comp;
                if (write_alpha < 0)
                    fwrite(&d[comp - 1], 1, 1, f);
                switch (comp)
                {
                    case 1:
                    case 2:
                        writef(f, (char *)"111", d[0], d[0], d[0]);
                        break;
                    case 4:
                        if (!write_alpha)
                        {
                            for (k = 0; k < 3; ++k)
                                px[k] = bg[k] + ((d[k] - bg[k]) * d[3]) / 255;
                            writef(f, (char *)"111", px[1 - rgb_dir], px[1], px[1 + rgb_dir]);
                            break;
                        }
                    /* FALLTHROUGH */
                    case 3:
                        writef(f, (char *)"111", d[1 - rgb_dir], d[1], d[1 + rgb_dir]);
                        break;
                }
                if (write_alpha > 0)
                    fwrite(&d[comp - 1], 1, 1, f);
            }
            fwrite(&zero, scanline_pad, 1, f);
        }
    }

    static int outfile(char const *filename, int rgb_dir, int vdir, int x, int y, int comp, const void *data, int alpha, int pad, char *fmt, ...)
    {
        FILE *f = fopen(filename, "wb");
        if (f)
        {
            va_list v;
            va_start(v, fmt);
            writefv(f, fmt, v);
            va_end(v);
            write_pixels(f, rgb_dir, vdir, x, y, comp, data, alpha, pad);
            fclose(f);
        }
        return f != NULL;
    }

#ifdef COMPILER_MSVC
    static int outfile_w(wchar_t const *filename, int rgb_dir, int vdir, int x, int y, int comp, const void *data, int alpha, int pad, char *fmt, ...)
    {
        FILE *f = _wfopen(filename, L"wb");
        if (f)
        {
            va_list v;
            va_start(v, fmt);
            writefv(f, fmt, v);
            va_end(v);
            write_pixels(f, rgb_dir, vdir, x, y, comp, data, alpha, pad);
            fclose(f);
        }
        return f != NULL;
    }
#endif

    int stbi_write_bmp(char const *filename, int x, int y, int comp, const void *data)
    {
        int pad = (-x * 3) & 3;
        return outfile(filename, -1, -1, x, y, comp, data, 0, pad,
                       (char *)"11 4 22 4"
                               "4 44 22 444444",
                       'B', 'M', 14 + 40 + (x * 3 + pad) * y, 0, 0, 14 + 40, // file header
                       40, x, y, 1, 24, 0, 0, 0, 0, 0, 0);                   // bitmap header
    }

#ifdef COMPILER_MSVC
    int stbi_write_bmp_w(wchar_t const *filename, int x, int y, int comp, const void *data)
    {
        int pad = (-x * 3) & 3;
        return outfile_w(filename, -1, -1, x, y, comp, data, 0, pad,
                         (char *)"11 4 22 4"
                                 "4 44 22 444444",
                         'B', 'M', 14 + 40 + (x * 3 + pad) * y, 0, 0, 14 + 40, // file header
                         40, x, y, 1, 24, 0, 0, 0, 0, 0, 0);                   // bitmap header
    }
#endif

    int stbi_write_tga(char const *filename, int x, int y, int comp, const void *data)
    {
        int has_alpha = !(comp & 1);
        return outfile(filename, -1, -1, x, y, comp, data, has_alpha, 0,
                       (char *)"111 221 2222 11", 0, 0, 2, 0, 0, 0, 0, 0, x, y, 24 + 8 * has_alpha, 8 * has_alpha);
    }

#ifdef COMPILER_MSVC
    int stbi_write_tga_w(wchar_t const *filename, int x, int y, int comp, const void *data)
    {
        int has_alpha = !(comp & 1);
        return outfile_w(filename, -1, -1, x, y, comp, data, has_alpha, 0,
                         (char *)"111 221 2222 11", 0, 0, 2, 0, 0, 0, 0, 0, x, y, 24 + 8 * has_alpha, 8 * has_alpha);
    }
#endif

// any other image formats that do interleaved rgb data?
//    PNG: requires adler32,crc32 -- significant amount of code
//    PSD: no, channels output separately
//    TIFF: no, stripwise-interleaved... i think

#endif // STBI_NO_WRITE
}
